Mario & Luigi: Bowser's Inside Story

Mario & Luigi: Bowser's Inside Story is a Nintendo DS game developed by AlphaDream and published by Nintendo. It was released worldwide in 2009 and in South Korea in 2011. It is the third title in the Mario & Luigi series, preceded by Mario & Luigi: Partners in Time for the Nintendo DS in 2005 and succeeded by Mario & Luigi: Dream Team for the Nintendo 3DS in 2013. The title of the game is a parody on the term "inside story", meaning the "true" tale of an event from the perspective of an insider who participated in the action, as opposed to an outsider who only hears about the event later on. In this case, the game is a literal inside story, as Mario and Luigi have to adventure through Bowser's insides. The game's European Spanish, European French, and Italian name is a parody on the famous novel . The original French name is Voyage au centre de la Terre, the Spanish name is Viaje al centro de la Tierra, and the Italian name is Viaggio al centro della Terra.

This is the only non-3DS installment in the Mario & Luigi series not to be released on the Virtual Console for the Wii U.

A Nintendo 3DS remake of the game, titled Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey, was released in Japan on December 27, 2018 and elsewhere in January 2019. Outside Japan, the release year marks the 10th anniversary of this game. This is the second game in the Mario & Luigi series after Mario & Luigi: Superstar Saga to have a remake.

Story
After the Mushroom Kingdom's citizens start contracting the blorbs, a disease that swells Toads, Princess Peach holds an emergency conference meeting at her castle, which includes Mario, Luigi, Toadbert, Toadsworth, and a Star Sprite named Starlow. Bowser crashes in and is sent flying out of Peach's Castle after easily being defeated by Mario. While in Dimble Wood, Bowser comes across a cloaked merchant, who is Fawful in disguise, that gives him a "Lucky Mushroom" that causes him to inhale his surroundings, then returns to Peach's Castle and uses this ability to suck in the characters attending the conference.

Mario, Luigi, and Starlow reawaken inside the Trash Pit area of Bowser's body, where they acquire hammers and use them to hit an exposed nerve and rouse Bowser, who had been dumped in Cavi Cape Cave. Starlow, who talks to Bowser throughout the game under the alias "Chippy", withholds information surrounding the Mario Bros.' whereabouts and assists him in remembering the past events. Bowser then encounters Fawful, who explains that the blorbs and the Vacuum Mushroom he gave Bowser were all part of a plan to conquer both the Mushroom Kingdom and Bowser's Castle. He then has his minion, Midbus, battle Bowser, where Midbus wins against him and abandon him.

Bowser helps a stranded Broque Monsieur get back on Plack Beach, where Broque rewards Bowser a Vacuum Block, allowing him to control his sucking abilities. After defeating the Sea Pipe Statue, Bowser drinks water which allows Mario and Luigi to enter the Pump Works and defeat the Scutlet bug that was blocking Bowser's fire breath at the Flame Pipe. After subduing Broque's pet dog Broggy, Bowser enters Dimble Wood, where he eventually comes across three of his minions: Sergeant Guy, Corporal Paraplonk, and Private Goomp. They plan to retake Bowser's castle with a Banzai Bill launcher, where Bowser is required to find ammunition. Bowser procures a giant carrot as a makeshift missile, but the owner, a Wiggler, makes him eat it and then attacks him. After he obtains the Banzai Bill from the Wiggler, Bowser is then overcome with stomach pain caused by consuming a parasitic Durmite along with the carrot; Mario and Luigi then defeat it in battle.

After his stomach issue is resolved, Bowser proceeds to launch the Banzai Bill towards Bowser Castle. However, Midbus dodges Bowser's Banzai Bill by launching the castle and landing it on Bowser. The Mario Bros. revive him from the Rump Command, which unintentionally turns Bowser as giant as the castle. After Bowser defeats the castle, it flies away with Bowser in pursuit, traveling through Bumpsy Plains and Bowser Path to reach the destination. Bowser deflects Midbus's iron ball, which knocks the castle down. Entering the castle, Bowser discovers that Fawful has turned it into a theater and brainwashed all the Koopa Troop members into a pack of his own adoring fans. Fawful himself arrives and tricks Bowser, forcing him to perform a cage match with Midbus on stage. When Bowser wins, his prize is being forcibly fed fattening foods cooked by Fawful, gaining so much weight that he breaks through the floor and becomes trapped.

Exploring the newly opened Flab Zone and defeating some Kretin enemies, Mario and Luigi are reunited with Princess Peach, who explains that Fawful is actually after the Dark Star, an evil entity locked away under Toad Town that can only be revived using Peach herself. Fawful then uses a laser to extract Peach from Bowser and he and Midbus leave with her, while Bowser falls the rest of the way through the floor onto a treadmill they placed beneath him in the basement. He literally burns off all the excess fat, igniting a crate of Bob-ombs in the process which sends him blasting off back to Cavi Cape. He meets up with some Monty Mole minions and helps them drill all the way to Toad Town, but when Bowser wanders into the corridor leading to the Dark Star, the security system activates and electrocutes him, rendering him unconscious.

Mario and Luigi gain access to the Pipe Yard in Bowser's body, which allows them to use warp pipes to return to the outside world. They emerge in the Toad Town Caves themselves and try to head off Fawful, but arrive too late. Fawful takes the Dark Star to Peach's Castle and uses its power to create a barrier preventing the Mario Bros. from following him. With no other option, they head to Dr. Toadley to try and do something about the blorbs problem instead, but Bowser arrives at the clinic as well and the three battle, with Bowser losing. Dr. Toadley then tells Mario and Luigi that they need to collect three Star Cures to cure the blorbs and possibly find a way into the castle. Bowser awakens, hears this, and rushes off, determined to find the cures before the Bros. Dr. Toadley then reveals to Mario and Luigi that the first cure is held by Durmite inside Bowser's body, and they head back in to get it. They locate Durmite immediately, but it flees through an impassable, Boo-like barrier, stopping the Mario Bros. in their tracks.

Meanwhile, Bowser heads to the shores of Blubble Lake, where his sneezes raise the propeller-topped Tower of Yikk out of the water and straight onto him. The Mario Bros. supersize Bowser again and he defeats the moving tower, venturing inside once he shrinks back to his regular size and meeting the ghost of Yikk, who shines his invention, the Boo-ray Machine, on Bowser's gut. The light from the machine causes the Boo-like barrier to disappear and help Mario and Luigi navigate the maze beyond them, allowing them to track down Durmite, who reveals herself to be a sage named Wisdurm. She battles them, turning to a butterfly after her defeat, dropping the Star Cure, and flying off.

Bowser leaves the tower and meets up with Private Goomp, who tells him that he already had one of the Star Cures locked away in his treasure chamber, having recently stolen it from an old Koopa named Kuzzle. Bowser returns to his castle, regaining access to his treasure vault by pushing a statue of Fawful through the barricades in the floor, only to find that the Monty Bros. were now under Fawful's control and had built a railway straight through the vault. They use their train to ram Bowser out of the castle and into a boulder, resulting in another emergency revival and giant battle between Bowser and the train. Returning to his vault after destroying the train, Bowser realizes that he has forgotten the combination to the safe that the Star Cure is stored in and asks "Chippy" to retrieve it for him. In the Memory Banks, Mario and Luigi have to defeat blocky doppelgangers of themselves, crafted from Bowser's own memories of them. After that, they reassemble a puzzle representing the memory and Bowser opens his safe, only to be pushed in by Private Goomp, Sergeant Guy, and Corporal Paraplonk, who had turned to Fawful's side. With nothing else to do in the cramped safe, Bowser eats the Star Cure, and it is retrieved from his gut by the Mario Bros.

Mario and Luigi return to Toad Town and are sent after the final Star Cure by Dr. Toadley. Guided by the doctor's messenger bird, Birdley, they meet the sage known as Chakron at the top of a cliff over Plack Beach, but he will only give them the Star Cure if they can knock him out of the pose he has held for a thousand years. After a cryptic hint from Chakron, Mario and Luigi head for Dimble Wood to collect Attack Pieces for the ground-shaking Snack Basket move, but Mario is kidnapped by a Sockop and has to be rescued by Luigi, who wears a knocked-out Sockop like a Goomba's Shoe to sneak into the enemies' territory. Reunited and having gathered all the pieces, the brothers return to Chakron and knock him over, so true to his word, he gives them the final Star Cure.

Back at the clinic, Dr. Toadley creates the Miracle Cure from the three Star Cures, which flies around ridding all the Toads of the blorbs and then allows Mario and Luigi to blast their way through the barriers to get to Peach's Castle. They search the gardens for a way in and are attacked by Midbus, who uses the remote-control Junker robot to fight them. The Mario Bros. win the battle, and the robot goes haywire, throwing the safe containing Bowser into a pile of garbage, breaking it open. Bowser's back seized up from being in the cramped safe for so long, so Mario and Luigi go back inside him to fix it, allowing him to break into Peach's Castle for them.

Bowser fights his way to Fawful and Midbus as they are slowly awakening the Dark Star. Fawful supercharges his minion into Blizzard Midbus, but Bowser wins the ensuing fight and Midbus's new ice powers end up freezing him solid. Bowser punches out Fawful as he tries to absorb the Dark Star's powers and he only gets a portion of it, with the rest of the revived evil entity forcing its way inside Bowser. Mario and Luigi chase the Dark Star around as it absorbs Bowser's DNA and takes on his characteristics, eventually emerging as an incomplete copy of Bowser, which sucks up Peach and floats off in search of the rest of its power. Bowser goes after it but is sidetracked by a final giant battle against Peach's Castle, which had been transformed into a giant robot by Fawful. He then battles Fawful himself, now souped-up by the Dark Star's powers into Dark Fawful. Bowser wins the fight and Fawful turns into a small ball of dark energy and tries to flee, but he gets absorbed by the Dark Star, allowing it to fully transform into Dark Bowser.

The real Bowser goes after his copy, chasing it to the tallest tower where it deposits the unconscious Peach before being confronted by Bowser, who aims to collect Peach, both castles and the Dark Star's powers. The final battle is waged on two fronts, starting off with Bowser fighting his clone, before punching it in the gut and forcing it to spit up Fawful. Bowser sucks up the little ball of energy and Mario and Luigi take over the fight, defeating both Fawful and the Dark Star Core inside Bowser. This leaves Dark Bowser unstable, and the real Bowser punches it until it explodes, freeing the Mushroom Kingdom from the Dark Star’s influence forever.

Inside Bowser, a battered and unstable Fawful appears in front of the Mario Bros., seemingly accepting defeat to them and saying that he will go away for good. However, he is actually faking it as he uses this opportunity to take the Mario Bros. with him in a final explosion of his own, all while sporting a large, dying grin on his face. All this accomplishes though is making Bowser eject everyone he had inhaled. The liberated Toads and the now-conscious Peach move to congratulate Mario and Luigi on a job well done, and Bowser, confused and angry, realizes that the brothers had been inside his body the whole time. Starlow dismissively tells Bowser to not worry about what's in the past but discovering that she was his supposedly loyal minion "Chippy" throws him into a complete rage. The Toads and the Princess flee from the scene, and the credits show a montage of still images showing that Bowser loses the ensuing fight.

Afterward, the heavily-injured Bowser is seen lying in bed at his castle while Private Goomp, Sergeant Guy, and Corporal Paraplonk beg him for forgiveness over their treason. Birdley arrives with a package from Peach, but when Starlow pops out of it to check in on him, Bowser angrily tells her to leave, as he is too busy fixing his castle to attack again anytime soon. He then lets the trio rejoin the rest of the Koopa Troop in helping with the repairs, and only once he is sure he is alone does Bowser open the package, revealing a thank-you cake with his face, Mario, Luigi, and Peach on it.

As in the other Mario & Luigi games, there is no "Endless Play" feature. As such, if the player plays the game after it is beaten and the ending is done, the game just starts from the last save point, before the final battle.

Battle system
The battle system of Mario & Luigi: Bowser's Inside Story is similar to that of its predecessors. There are some new additions to the system. In this installment, all Action Commands are evaluated based on how well they are performed. There are five evaluation levels. Ranging from the worst to the best, these levels are: Nothing, OK, Good, Great, and Excellent. The better an Action Command is performed, the more damage an attack does. Receiving a Nothing is equivalent to not performing an Action Command at all. This is carried into all the later installments of the series.

Stats
Each brother and Bowser have their own HP, SP, POW, DEF, and SPEED, as well as STACHE points for the brothers, and HORN points for Bowser. When they finish a battle, they each gain EXP Points and coins. With enough Experience Points, they can level-up and increase each respective statistic.

Mario and Luigi's battle system
The battle system with Mario and Luigi is similar to the battles from the previous games. There are now six categories of attack during battle, as opposed to Mario & Luigi: Partners in Times five, or Mario & Luigi: Superstar Sagas four. These are Jump, Hammer, Attack Pieces (Bros. Items), Items, Bros. Badges, and Escape. The Bros. can defend with their jump and their hammers. The Jump makes Mario and/or Luigi jump to dodge an attack or to counter-attack. The Hammer is used to counter-attack. The music played while battling is the same as the music played during the debut trailer, as seen in the Japanese site.

A new element has been added to battles, a gauge at the bottom of the screen with Mario and Luigi's heads on either end. When Mario or Luigi pull off an action command, that brother's end of the bar fills slightly. When they meet in the middle, it is possible to use a Bros. Badge move. The effect varies with the equipped badge. The normal effect is to restore 20% of both brothers' HP. Badges can be bought in one of the shops in Toad Town. Some of the badges require that the Action Commands be pulled off perfectly (EXCELLENT is displayed), and some only need GOOD!. An extra block that appears in the battles can be used to swap the badges that brothers use.

Bowser's battle system
Bowser has almost the same battle system as Mario and Luigi's, but with a few differences. He has different options: Punch replaces Jump, Fire Breath replaces Hammer and Enemy Attacks replace Special Attacks. However, he does not have Bros. Badges. Instead, Bowser gains a vacuum ability after the player advances further through the game. He can swallow enemies with this new ability to make Mario and Luigi fight them in his belly. He can also swallow parts of enemies that can restore his HP, raise defense or attack power, or rescue a Blitty. Bowser's defenses are the Punch and the Shell. Bowser's Punch can counter-attack an enemy, while his spiky shell can hit enemies that try to jump on his head or protect him from attacks.

Enemy Attacks are special attacks that use mostly members of Bowser's army, which are Goombas, Koopa Troopas, Shy Guys, Bob-ombs, Magikoopas, and Broggy. These attacks require the stylus to perform. These characters need to be liberated to unlock these attacks.

Bowser Specials
Bowser has six Special Attacks, five of which are obtained via destroying cages contained Bowser's trapped minions. * - Required

Mario & Luigi Specials
Mario and Luigi obtain these special attacks via Attack Pieces found by hitting a Attack Piece Block and numerous other ways. * - Required

Giant Bowser battle system
At certain points in the game, Bowser gets crushed by a large object such as Bowser's Castle. In order to revive Bowser, the Bros. must play a 2D-Shooter-like minigame in the Rump Command. When revived, Bowser grows to a giant state. In order to complete these battles, the player must rotate their DS sideways to play. In these battles, Bowser only has three options of attack. Punching requires quickly sliding the stylus across the screen to execute. Fire requires the player to blow into the DS microphone. The last option, Healing, requires Mushrooms found within the battle itself. Defending includes an event where the player must tap the touch screen in certain areas to counter-attack, punching to deflect blows, and blowing huge flames at the enemy. After each giant battle, Bowser returns to normal. There are four such battles in the game.

Ranks
When leveling up Mario and Luigi, and Bowser occasionally reach a rank. When this happens new criteria is added to the game such as being able to equip more clothing or being able to shop at certain places. Here is a list of the ranks:

Mario & Luigi Bowser

Key items
There are many items that appear in the game that the heroes must obtain in order to advance in the game. Most of these items require the players to go through some trial, whether it be a challenge, facing a boss, or through other means.

Consumable items
These are the items that appear in Mario & Luigi: Bowser's Inside Story. Please note that some of the items used in this game have appeared in the previous installments.

Clothing
Mario & Luigi: Bowser's Inside Story differs from its predecessors by including a more varied clothing system. In addition to overalls, Mario and Luigi can wear socks, gloves, boots, and accessories while Bowser can wear shells, arm bands, rings, and fangs. Mario, Luigi, and Bowser can wear additional clothing types if they rank up from repeated battles.

Badges
Badges in Mario & Luigi: Bowser's Inside Story are used exclusively by Mario and Luigi, and they work differently from its predecessors. Mario and Luigi must successfully perform Action Commands to fill the badge gauge. Once the gauge is filled, players can tap it to receive an effect that benefits them in a variety of ways, which can be changed depending on the type of badge both brothers wear.

In the table, the left side of the badge (Luigi's badge) decides how good the action command must be to fill the bar, and how big the effect will be. The right side (Mario's badge) decides what the effect will be.

Status ailments
Many status ailments appear in Mario & Luigi: Bowser's Inside Story. Each type affects the heroes and enemies with their own variables. Many enemies can inflict the diseases, as well as some attacks that the three heroes can learn. To relieve the effects, the player can use a Refreshing Herb or - depending on the type - can wait for it to run out of their systems.

Supporting

 * Princess Peach
 * Toadsworth
 * Toadbert
 * Starlow
 * Kamek
 * Toads
 * Broque Monsieur, a bipedal creature who seems to be made from ? Blocks.
 * Broggy, Broque's pet.
 * Broque Madame, another bipedal creature made out of ? Blocks.
 * Blitties, cat creatures that seem to also be made out of ? Blocks.
 * Three members of Bowser's army:
 * Sergeant Guy, a green Shy Guy with a bag on his back containing a gray pipe and a Magikoopa's wand.
 * Corporal Paraplonk, a red Paratroopa wearing a red bucket on its head and green shoes.
 * Private Goomp, a Goomba that wears blue clothes and seems to look sad.
 * Emoglobin, a species of block-like creatures inside Bowser that give hints and help with minigames.
 * Princess Lipid, who explains Bros. Badges.
 * Yikk, the creator of Tower of Yikk and the Boo-ray Machine.
 * Kuzzle, the guardian of the second Star Cure.
 * The Koopa Paratroopa Trio, friendly blue-shelled Paratroopas.
 * Dr. Toadley, the Toad with a Miracle Cure.
 * Chakron, the guardian of the third Star Cure.

Bestiary
Note that stats listed there are from the North American version of the game. Stats with the Challenge Medal and other versions may vary.
 * i Indicates they can be inhaled by Bowser and then fought by Mario & Luigi.
 * m Indicates only Mario can battle them.
 * m&l Indicates only Mario & Luigi can battle them.
 * b Indicates only Bowser can battle them.

Inside Bowser
All enemies here can be battled with Mario & Luigi.

Bosses
The following is a bestiary for all bosses encountered in the game Mario & Luigi: Bowser's Inside Story. Please note that some of the bosses are fought necessarily; some are optional, such as the X bosses; and some require Bowser to become giant to brawl them.
 * e Indicates the battle automatically ends after several turns.

Normal Bosses

 * Boss Support

Giant Bosses
All these bosses can only be battled with Giant Bowser.

Gauntlet Bosses
Note that all X bosses only awards coins on their first defeat. All these bosses are fought by Mario & Luigi.


 * Boss Support

Overworld
While Mario and Luigi adventure through Bowser's body, Bowser is walking around the overworld. Mario and Luigi can influence Bowser. They can pinch nerves to make Bowser panic. They can also touch Bowser's muscles to give him a power-up. Equally, Bowser can change the course of the Mario Bros.' adventure. For example, he can flood them by drinking from a fountain. After a certain point in the game, Mario and Luigi can go to the Pipe Yard and use Warp Pipes to exit Bowser's body and explore the overworld, and then use the pipes to enter Bowser's body again. Bowser can use Chakroads to warp between different locations of the Mushroom Kingdom.

Overworld icons have slightly changed. They now display the health of the character. Bowser uses two buttons in the overworld, X to punch, and Y for firebreath. Later in the game, Bowser learns new moves such as a dashing punch, ground-pounding, and curling up into a spikeball (much like the way he attacked Mario in Super Mario Galaxy). Mario and Luigi use A and B respectively to jump. At one point they gain hammers. Mario can destroy rocks and crates, while Luigi can hit Mario to make him mini so as to reach previously inaccessible areas. Later in the game, the Marios learn new moves such as the Spin Jump and the Drill Bros. They also encounter items in the overworld that help them perform moves to reach a goal or an item. The items include a gas pump that seems to be shooting out helium. Mario can fill himself up with helium and float into the air like a balloon. If Luigi is to grab his legs at that time, they are able to perform a floating high jump, somewhat similar to the move found in the first installment of the series. They can also find a Blue Koopa shell that Mario can put on. Luigi can whack him with his hammer to shoot Mario over previously inaccessible areas to hit switches. This move is very similar to the move the Koopa companions use in the Paper Mario series.

While Bowser explores a 3-D overworld, Mario and Luigi explore a 2-D world inside his body, much like a traditional platformer, though they can go into the 3-D overworld at any time once the Pipe Yard is available. The actual overworld is connected just as it was in Mario & Luigi: Superstar Saga, unlike Partners in Time's linear levels. The overworld is up to 4-5 times larger than Superstar Saga's overworld. The map in this game consists of a beach, a forest, a cape, the road to Bowser's Castle, Toad Town, Bowser's Castle, Peach's Castle, Grasslands, a railroad, underground, and a lake. In the Nintendo Power review, it was stated that there are tons of sidequests, much to explore, and plenty to do in the free roam overworld.

Locations
* Only Mario & Luigi can access. ** Only Bowser can access.
 * Mushroom Kingdom
 * Peach's Castle
 * Dimble Wood
 * Cavi Cape
 * Plack Beach
 * Bumpsy Plains
 * Bowser Path
 * Bowser's Castle
 * Tunnel**
 * Toad Town
 * Toad Town Mall*
 * Tower of Yikk
 * Blubble Lake
 * Project K**
 * Peach's Castle Garden


 * Bowser's body
 * Trash Pit
 * Funny Bone
 * Toad Square
 * Challenge Node
 * Arm Center
 * Pump Works
 * Flame Pipe
 * Gut Check
 * Nerve Cluster
 * Rump Command
 * Flab Zone
 * Pipe Yard
 * Leg Outpost
 * Nose Deck
 * Energy Hold
 * Joint Tower
 * Memory Banks
 * Lumbar Nook
 * Chest Station
 * Airway

Shops
Throughout the game, there are several shops where the player can purchase and sell items from several shops on their adventure. Shops available to Mario and Luigi are run by characters and all found in Toad Town Mall and Toad Square. Only two shops are available to Bowser: Broque Monsieur's Shop and Broggy's Shop, both in Dimble Wood. However, there are Shop Blocks around the Mushroom Kingdom that provides the same functionality to Bowser. There is a Scratch Card system where the player has a chance to get a part of their coins spent back. The amount of squares that give coins back depends on Mario and Luigi's stache level and Bowser's horn level.

Beans
After Mario and Luigi learn the Drill Bros. move, they can collect beans from beanholes by tunneling underground and then jumping. There are about 200 beanholes scattered around the world, both in the Mushroom Kingdom and inside Bowser's body. Mario and Luigi can also collect beans from characters like Kuzzle and the PR Toad of Toad Town Mall.

Differences from other Mario & Luigi games
While a direct sequel in the Mario & Luigi series, Mario & Luigi: Bowser's Inside Story still has several differences compared to the first two Mario & Luigi games.
 * This is the first game to feature more than one optional boss stronger than the final boss.
 * This is the first game in the series not to feature Professor E. Gadd, or Yoshi.
 * This is the only game in the series to feature Bowser as a main protagonist.
 * This is the first Mario & Luigi game to give Mario and Luigi's in-game sprites eyebrows.
 * This is the first game in the series where Mario and Luigi can double jump; in battle in the first game, they could not while in the second game, they needed the babies to do it.
 * This is the only Mario & Luigi game to not have any traditional enemies as common enemies, besides derived species which only appear in this game.
 * This is the first Mario & Luigi game to feature an "Excellent!!" rating when completing an attack.
 * This is the first Mario & Luigi game where jump and hammer attacks receive a rating depending on how well timed the attack is.
 * This is the only Mario & Luigi game to not have a purely snow-, desert-, mountain-, or temple-themed area.
 * The Airway can be considered a snow- or ice-like area when it is frozen, and Plack Beach features a mountainous section.

Gameplay differences

 * This is the first Mario & Luigi game to have optional bosses, with the exception of three of the four Popple fights and Jojora in Mario & Luigi: Superstar Saga, who are not required to be defeated, but can be defeated for extra experience and items.
 * Unlike Mario & Luigi: Partners in Time for the Nintendo DS, this game makes greater use of the DS's touch controls and microphone.
 * This is the first game in the Mario & Luigi series (as well as the fourth RPG overall) to have Bowser as a playable character.
 * The player can equip Mario and Luigi with pants, gloves, shoes, socks, and accessories instead of just pants as in the first two Mario & Luigi games.
 * Badges have a different function. Bro. Badge moves can be performed with them. This game contains eight badges, which is notably less than the previous Mario & Luigi games.
 * This is the first of the series to have power-ups or other items in the overworld such as the blue Koopa Troopa shell.
 * This is the first Mario & Luigi game to have a rank system. This means, if the player gets at a certain level, they go to a higher rank. Ranks for Mario and Luigi are the Mushroom Rank, Shell Rank, Flower Rank, Shine Rank, Star Rank, and the Rainbow Rank. Bowser's ranks are the Bronze Boss Rank, Silver Boss Rank, Gold Boss Rank, and the Final Boss Rank.
 * Mario and Luigi get the hammers earlier in Mario & Luigi: Bowser's Inside Story than in the other Mario & Luigi games. (An exception is Mario & Luigi: Paper Jam, where they have hammers from the start.)
 * The Scratch Card is introduced, allowing the main characters to earn back coins after spending them.
 * This is also the first game where the hammerheads do not fall off in defense when held too long; the bro. just puts it down. Consequently, the hammer can also be held much longer.
 * In the first two games of the series, Mario and Luigi use a suitcase to store anything they collect in their journey. In Bowser's Inside Story, however, they use the star menu, managed by Starlow in order to access their items.
 * This is the first game to have a Boss-Refight or Skill Challenge.
 * This is the first time in the Mario RPG series that a sequel has been released on the same system as its predecessor.
 * This is the second game where the Mario Bros. battle inside Bowser's body, the first being Mario & Luigi: Superstar Saga, where they battle Cackletta's Soul inside Bowser. Fawful (who worked for Cackletta) is fought in a similar way to Cackletta. Also, before both battles take place, the player fights an affected form of Bowser. While Mario and Luigi are sucked into Bowser and Cackletta was inside him, for Fawful it is the reverse; Bowser inhales Dark Fawful, and he fights the Mario Bros. inside of Bowser.
 * This is the first Mario & Luigi game where Bowser does not end up possessed by the main villain, as well as the first RPG game since Paper Mario where the main villain does not actually possess one of the main characters.
 * However, Dark Bowser is a character who has copied Bowser lineaments by gathering his DNA, and is similar to previous Bowser possessions.

Release differences

 * This is the first Mario & Luigi game to be released in Japan before any other country.
 * This is the first Mario & Luigi game in which the American box art is the same as the Japanese box art. The European box art, while not exactly the same due to the ratings' graphics requiring the artwork to be rearranged, uses the same artwork (but with Luigi's and Bowser's eyelines changed to reflect their positions) and background as the Japanese box art.
 * This is the first Mario & Luigi game to have multiple languages for its North American release. Both the French and Spanish translations are distinct from those of Europe.

Staff
The game's producers were Toshiharu Izuno, Akira Otani, and Yoshihiko Maekawa, with Shigeru Miyamoto and Takashi Tezuka acting as senior producers and Satoru Iwata and Tetsuo Mizuno acting as executive producers. The game's director was Hiroyuki Kubota and Makoto Aioi was the main programmer.

Reception
Mario & Luigi: Bowser's Inside Story has received critical acclaim, with a score of 91.01% based on 47 reviews on GameRankings and a 90 based on 58 reviews on Metacritic, making it the highest-rated out of the Mario RPG games. Much of the game's praise was directed towards its gameplay, humor, storyline, integration of Bowser as one of the main protagonists, and innovative use of the Nintendo DS's capabilities.

Sales
Bowser's Inside Story has sold 3.81 million copies worldwide as of April 2016, making it the best-selling RPG in the Mario franchise.

Mushroom Kingdom Tribune
The Mushroom Kingdom Tribune was a promotional newspaper sent by Nintendo via e-mail. This newspaper included information about the release of Mario & Luigi: Bowser's Inside Story.

This newspaper included "Reviews from the Mushroom Kingdom", which are quotes from the game characters:
 * "I have chortles!" - Fawful
 * "Did someone just page the King of Awesome?" - Bowser
 * "SUPER ULTRA WONDER ULTIMATE RUTHLESS GREAT IRON BALL!" - Midbus

Bowser

 * "Did somebody page the king of awesome?"
 * "MAAARIO! Are you seriously trying to start with me again?! I hear about this big meeting, and I'm all ready to act nice... But man, the second I see your face, Mr. Nice Bowser is GONE. Yeah, forget your dumb meeting! I'll pummel you and grab Peach!"
 * "GWAHAHA! Great dark hurricane! Seriously, perfect backdrop for an awesome final battle! You really sweat the details! Listen up! You're saying the kingdom will vanish? NOT TODAY! THIS KINGDOM IS ALL MINE! SO YOU VANISH!"
 * "SHOWTIME!"

Fawful

 * "All who resist will be beat like naughty little eggs!"
 * "Beef? I am lacking in beef. Fawful is beefless."
 * "Fawful sings a song of bad!♪ The Mushroom Kingdom is so sad!♪ All of it is for Fawful!♪ And the...rhyme...with that!♪"
 * "Here Fawful goes, the disappearing..forever disappearing... WITH YOU!"
 * "I HAVE CHORTLES!"

Pre-release and unused content
Some enemies have an attack pattern for Mario and Luigi, even if they do not face them in the game. There are also several unused voice clips for Yoshi, coming from Yoshi's Story; there is also unused music from Mario & Luigi: Partners in Time, although it will not play correctly. Early screenshots also show Treevils being battled at Plack Beach.

Glitches
Before the fight with Scutlet if the players re-enter the Pump Works and hit the Save Block the message will say that Bowser can breathe fire again, even though the Flame Pipe is still blocked.

References to other games

 * The Legend of Zelda - In Toad Town, Mario and Luigi meet a Toad who teaches them how to dig up special beans. After finishing, he states, "Find all you can. They're a secret to everybody!", in reference to the saying in this game where the Secret Moblin would give Link free Rupees after saying, "It's a secret to everybody."
 * Super Mario Bros. 2 - During Bowser's battle with the giant Wiggler, the Wiggler sometimes attacks by pulling out vegetables, which are the same ones that are seen in this game. Also, one of Bowser's brainwashed minions states that he forgot what Bowser's castle was originally called (before it was turned into "Fawful Theater"), and mistakenly referred to it as "Mouser's Castle".
 * Super Mario RPG: Legend of the Seven Stars - In addition to the storyline of Bowser attempting to reclaim his castle, Bowser states that Chippy could be an honorary member of the Koopa Troop, and she could "thank him later" (just like when Bowser rationalizes joining Mario's party). In addition, some notes of the Forest Maze track appear in the Toad Town and Peach's Castle themes.
 * Super Mario Bros. 3 - The starting section of the file select music is similar to the P Switch and Toad House theme. Sockops are clearly meant to resemble the Kuribo's Shoe, and at one point Luigi will even hop around inside an unconscious Sockop, allowing him to walk along spikes without taking damage, just as the Kuribo's Shoe does. In addition, one of the Sockops' names is, apparently, Kuribo.
 * Dr. Mario - Blue Viruses appear on a poster in Dr. Toadley's office, and in one of the Toothy's attacks.
 * Super Mario World 2: Yoshi's Island and Yoshi's Island DS - The Fawful Guy enemy can imitate the attack patterns of both the Woozy Guy and the Glide Guy. In addition, one of its attacks mirrors Yoshi's main form of offense in the game, egg throwing.
 * Super Mario 64 - The music that plays within Peach's Castle when visiting it for the first time is a variation of its theme here.
 * Super Mario Sunshine - One of the brother's ranks is called the Shine Rank.
 * Paper Mario - The Koopa Paratroopa Trio in the game wear sunglasses, similar to this game. The blue Koopa shell power-up in the overworld is similar to Kooper's field ability. Also, Princess Peach using her combined powers with Starlow references Peach Beam.
 * Mario & Luigi: Superstar Saga - Fawful reappears as a villain. The way Bros. Attacks are used from this game is reused, and there is a slight remix of Cackletta's theme song that played in the background after Fawful took over Peach's castle. Mario and Luigi battle Dark Fawful inside of Bowser's body, just as they did with Cackletta. The chair seen near the Conference Room has the same design (seen only briefly in the beginning of said game). Also, the Mini Mario and Spin Jump abilities return.
 * Mario & Luigi: Partners in Time - When Mario and Luigi talk to Broque Madame, she tells them stories about the Shroob invasion that took place in the game. Several Shroobs are also seen at Bowser's castle, where they were kept frozen in a cryogenic chamber. If the player chooses to thaw them out, then an optional boss battle with them will commence. During the battle, several other Shroobs, including the Elder Princess Shroob can be seen in the background. After the battle, Mario and Luigi tell Starlow about their previous battle with the Shroobs, and how they defeated them while they were babies. While the audience is still in the theater in Bowser's castle, a Shroob can also be found sitting in the audience on the bottom right. Also, there is a boot called the Shroob Boots. Fawful Guys, which are fought by Mario and Luigi in Bowser Path, have an attack in which they are pulled offscreen by a tongue (during which the same roar heard from Yoob is heard), and are thrown at either one of the bros. in the form of an egg, which highly resembles one of Sunnycide's attacks.
 * New Super Mario Bros. - Blue Shells make a reappearance, as does Shell Mario. A Mega Mushroom also occasionally appears during one of Broque Monsieur's attacks in his tutorial.
 * Super Paper Mario - Bowser's battle animation resembles the one in this game.
 * Super Mario Galaxy - Spike Ball, the ability where Bowser curls into a ball, heavily resembles an attack that Bowser uses during his fights against Mario/Luigi.

References in later games

 * Mario & Luigi: Dream Team - Starlow, Broque Monsieur, Broque Madame, Broggy, Private Goomp, Corporal Paraplonk, and Sergeant Guy all return to this game. Also, Bowser's theme is reused. The boxart style is reused.
 * Super Smash Bros. for Wii U - The songs "Tough Guy Alert!" and "The Grand Finale" return in this game.
 * Nintendo Badge Arcade - One of the badges in the Pixel Collection set depicts the Mario & Luigi: Bowser's Inside Story game card.
 * Super Smash Bros. Ultimate - The songs "Tough Guy Alert!" and "The Grand Finale" return in this game. Fawful, Starlow, and Broque Monsieur (using their respective artwork from this game) appear as spirits.

Trivia

 * The game's title is changed in the Italian, European French and European Spanish localizations. It can be re-translated to English from all three languages to "Mario & Luigi: Journey to the Center of Bowser", referencing Jules Verne's science fiction novel Journey to the Center of the Earth.