“Seriously, though, who would actually believe that mansions get given away in contests?! Talk about stupid! What do they feed you Mario brothers anyway... gullible soup?”
King Boo (Japanese: キングテレサ King Teresa) is the leader of the Boos and the main antagonist of the Luigi's Mansion series, and is the arch-enemy of Luigi. He is also an ally of Bowser, who has aided him in his various schemes. He is more than capable of devising and enacting villainous plans by himself, including his capture and imprisonment of Mario. Although not the biggest Boo in the Mushroom World, King Boo has abilities that far surpass that of the average ghost and he wields a number of impressive magical abilities, including the ability to materialize objects. King Boo's magical power is directly proportional to the number of Boos in his vicinity.
 Luigi's Mansion
Before the events of Luigi's Mansion, Professor E. Gadd captured Boolossus. Using a device called a Ghost Portrificationizer, E. Gadd trapped Boolossus in a portrait and hung it in his Gallery inside his lab in Boo Woods. This angered King Boo, so he devised a plan to rescue Boolossus.
King Boo and his forces attacked the laboratory. The Boos reversed the settings of the Portificationizer and released Boolossus. King Boo then ordered that all the ghosts that E. Gadd had captured should be released as well. After releasing all the portrait ghosts, King Boo created a huge mansion and placed it next to the professor's lab. King Boo, his Boo minions, and the recently freed portrait ghosts decided to inhabit the mansion. With a huge mansion and an army of ghosts, King Boo decided to exact revenge upon Mario and Luigi by capturing them.
Hoping to recapture Luigi, King Boo sends him a letter. The message states that Luigi has won a mansion in a contest and provides the location of the prize. Luigi asks his brother Mario to investigate the mansion and says that he will arrive shortly thereafter. Mario and Toad travel to the mansion, but right after Mario enters, he is instantly overwhelmed by King Boo's forces and captured. King Boo then imprisons him in a portrait, similar to how Boolossus was imprisoned. Mario is placed in the Secret Altar in the basement of the mansion. With Mario captured, King Boo is ready to capture Luigi.
While waiting for Luigi, King Boo and his Boo minions wait behind a secret door in the floor of the Storage Room. When Luigi enters the room and reveals the secret door, the Boos spring out from the floor. However, the Boos (including King Boo) stop their surprise attack when they notice the Poltergust 3000 on Luigi's back. Luigi had been given the Poltergust 3000 by E. Gadd so he could recapture the Portrait Ghosts and save his brother. The Poltergust 3000 is one of the few things King Boo fears, and he and the other Boos scatter and hide in the mansion. King Boo travels to the Secret Altar in the mansion's basement.
The special key that Vincent Van Gore holds unlocks the path to the Secret Altar. However, he is locked in the Artist's Studio on the third floor of the mansion. After capturing him and retrieving the key, Luigi discovers that he still cannot enter the Secret Altar. If Luigi attempts to enter the Secret Altar without catching a certain number of Boos, King Boo blows Luigi to the Foyer, the entrance of the mansion. Since King Boo's power is related to the number of Boos in the mansion, Luigi can weaken him by capturing the Boos hidden in various rooms. After Luigi captures at least forty of the mansion's fifty Boos, King Boo loses his ability to blow Luigi from the Secret Altar. Once King Boo is weakened, Luigi enters King Boo's Secret Altar.
Upon entering the Altar, Luigi notices King Boo staring at Mario in the painting. King Boo turns around to face Luigi and states his desire to add a Luigi painting to the collection. After this, King Boo flies into the Mario painting hanging on the wall. The picture of Mario transforms into Bowser, then the new Bowser painting inhales Luigi into the canvas, transporting Luigi into an arena that resembles the mansion's roof. Luigi then confronts Bowser. In reality, this is a illusion of Bowser that King Boo controls from the inside and uses as a shield.
King Boo uses this Bowser illusion to attack Luigi, shooting flames at him, and even attempting to inhale him into its mouth. The illusion also has the ability to create three large spiked bombs and toss them at Luigi. Luigi can use his Poltergust 3000 to grab one of the spiked explosives and release it into the illusion Bowser's mouth. This attack blasts the head off of the illusion Bowser, causing King Boo to exit the illusion shield and expose himself to the Poltergust 3000. Luigi begins to deplete the ghost's five hundred hit points. Meanwhile, the illusion's head hovers around the arena, shooting icy blasts at Luigi. Eventually, King Boo flies back into the dormant Bowser body and the head reattaches itself, resuming the fight. Luigi repeats this process, slowly weakening King Boo, but after King Boo's life falls below two hundred HP, the head of the illusion reattaches backwards whenever he returns to the Bowser body, causing the illusion Bowser to run around aimlessly. Eventually, the illusion turns its head forwards and resumes the fight. Eventually, Luigi manages to completely drain King Boo's HP and capture him inside the Poltergust 3000.
After the battle, Luigi receives King Boo's crown, worth 5000G, and adds it to his treasure collection. Upon returning to the mansion, Luigi quickly travels to Professor E. Gadd's lab. In the lab, Luigi connects the Poltergust to the professor's Portrificationizer, dumping its contents into the machine. Oddly, not only does the spirit of King Boo appears in the Portrificationizer, but also the Bowser illusion. With King Boo captured, Professor E. Gadd hangs his new portrait in an empty room in his gallery.
 Luigi's Mansion: Dark Moon
King Boo reappears in the 3DS game, Luigi's Mansion: Dark Moon once again as the main antagonist and final boss. Appearance-wise, he is much similar to his appearance from Luigi's Mansion, but retains the full set of teeth and sped-up voice he had in his appearances in the other Mario titles and he is also much larger.
It is revealed later in the game that Professor E. Gadd had sold the portrait of King Boo from Luigi's Mansion at a garage sale (a car boot sale in PAL versions), which is how the King escaped. King Boo shatters the Dark Moon into six pieces with a bolt of energy from his crown, which contained a power-enhancing gem. This turns the once-friendly ghosts of Evershade Valley hostile and mischievous as well as sprawling the Dark Moon's pieces to each Mansion of the valley, which Luigi has to recover.
Towards the end of the game, it is revealed that he has captured Mario once more. After Luigi gets the last Dark Moon piece and returns to the Bunker, he captures Luigi and pulls him back into the Paranormal Dimension. He reveals to Luigi he escaped from the painting and broke the Dark Moon, causing the ghosts to become under his control. He intends to use the ghosts as an army to conquer the world. He also plans to put Luigi and E. Gadd into paintings as well for revenge. He then engages into battle with Luigi but he fails and is sucked into the Poltergust once again.
 Super Mario series
 Super Mario Sunshine
A different "King Boo" is the leader of the Boos on Isle Delfino and appears as a boss in Sirena Beach, the sixth world of Super Mario Sunshine. He is apparently made from yellow goop, as can be seen during his defeat, meaning that Bowser Jr. might have drawn him. This game also notes that he dislikes spicy food, which serves as the key to defeat him.
He is named King Boo by the American localization team. However, the original Japanese version assigns a unique name to this character (ボステレサ, meaning Boss Boo), signifying that this King Boo is a separate character from the King Boo that appears in Luigi's Mansion and all other games.
 Super Mario 64 DS
King Boo appears in the Super Mario 64 remake, Super Mario 64 DS. As the boss who locked Luigi away, he captures a part of Princess Peach's Castle. However, in the English version of the game, King Boo is incorrectly called Big Boo, even though the Big Boo from the original game also appears in the game.
Regardless, King Boo aids Bowser in his conquest of Peach's Castle by capturing Luigi and imprisoning him in Big Boo's Haunt. Specifically, Luigi is imprisoned behind a painting of himself inside the haunted mansion. Mario heads to the Big Boo Battle level to save Luigi. Upon entering the level, he is greeted by King Boo, and from there he must listen for King Boo's cackle and enter the door where it is loudest. Eventually Mario reaches the end and fights King Boo to free Luigi. To defeat King Boo, Mario has to follow King Boo's movements in the arena's mirror and stomp him when he comes close enough. Ultimately, Mario saves his brother from King Boo and together (with Yoshi and Wario once he is saved) they defeat Bowser and save Princess Peach.
 Mario Kart series
 Mario Kart: Double Dash!!
King Boo is an unlockable character in the racing game Mario Kart: Double Dash!!. This is his first appearance in a spin-off, and also his first playable appearance. His appearance in this game results in his frequent appearances in the Mario Kart series, as he appears in Mario Kart DS as a boss and in Mario Kart Wii as a playable character again. Despite being a ghost, King Boo is classified as a heavyweight driver due to his large size. His partner is Petey Piranha, and both have the ability to use any other character's special item (if they are going to get a special item, it is randomly chosen, based on their race position). Of course, this means that they possess no unique special item of their own.
King Boo's personal kart is the Boo Pipes, which is a gray version of Petey's Piranha Pipes kart, but with an image of a Boo instead of a Piranha Plant where the item-using partner stands. However, the more important difference between the two is that, while the Piranha Pipes has high speed and low acceleration, the Boo Pipes is vice versa, with low speed and high acceleration, which is quite odd for a heavy kart. In fact, the only other heavy kart like this is the Offroader from Mario Kart Wii.
Oddly, when partnered with Petey Piranha, King Boo appears smaller than Petey. This is most noticeable before the race starts if he is not the driver. Yet, if partnered with another character, he appears much larger than the other character. He also appears to slightly shrink when he becomes the driver. On the second "Thanks for Playing!" screen (after beating the Special Cup with a Gold Trophy while all other cups already have a Gold Trophy), King Boo appears in the background, chasing Wario and Waluigi.
 Mario Kart DS
In Mario Kart DS, King Boo, along with six other bosses from Super Mario 64 DS, appear as the bosses of the Mission Mode. King Boo is the boss of the fourth level, with the playable character being Peach. Peach attempts to collect fifty coins on the Lava Arena within the time limit, but after a few seconds King Boo appears, surrounds her, and then attacks her, stealing ten of her coins and making all the other, uncollected coins disappear, before teleporting to another area of the arena. To take them back, Peach has to drive and bump into King Boo, making him transparent. Then, she can drive through him again, retrieving her coins and making the other coins reappear. However, King Boo soon reappears a few moments later to get the coins again. After collecting all fifty coins, Peach finally defeats King Boo.
 Mario Kart Arcade GP 2
King Boo makes a cameo appearance in Mario Kart Arcade GP 2 on the Yoshi Park 2 course in the Horror House. Here, a large picture of him appears near the end of the course where it inhales many ghosts and the racers. As the player drives into his mouth, they warped back to the beginning of the course.
 Mario Kart Wii
King Boo returns in Mario Kart Wii as a large-sized driver, and is unlocked by completing the Star Cup in 50cc. He features a good handling bonus and a small off-road bonus, which comes in handy for vehicles like the Offroader, Wario Bike, and Phantom. He is used as the Staff Ghost on the SNES Ghost Valley 2 course. In the credits, he appears driving the Jetsetter on the SNES Ghost Valley 2 course.
King Boo is one of very few characters to have his standing animation on the Character Select screen altered from Mario Kart: Double Dash!! In this case, his tongue is not sticking out of his mouth the whole time like before; now, before selecting him, his tongue is still in his mouth. Other characters whose sprites were altered include Birdo, whose bow was made larger, Wario, who now has short sleeves, and Waluigi, who, when selected, does something somewhat different from what he did before.
 Mario Baseball series
 Mario Superstar Baseball
King Boo is a playable character in Mario Superstar Baseball and a member of Wario's baseball team, the Wario Greats. He does not need to be unlocked. He is a power hitter, using his white, crowned, Boo-like baseball bat to hit long outfield drives and even homeruns. King Boo has chemistry with Boo and Petey Piranha, and he has bad chemistry with Luigi. However, like Boo, his hits are usually very curved, and this causes them to be fouls most of the time.
 Mario Super Sluggers
King Boo reappears in Mario Super Sluggers and is one of the few characters that were on Wario's team in the last game that are still on it. He is once again a power hitter, and he also excels in pitching, with both stats being his highest. In Challenge Mode, he appears immediately after the player defeats Bowser Jr. at the Wario City stadium, stating that he turned invisible and was watching the whole game. However, he is uninterested in joining the player's team unless the team has some Boos with them. This is accomplished by finding both Boo and the Mini Boos item. In this game, King Boo has chemistry with Petey Piranha, Boo, King K. Rool, and Wiggler, but he has bad chemistry with Mario, Luigi, Baby Mario, and Baby Luigi.
His baseball bat does not have a physical crown on it anymore. In this game, it is represented as a crown picture above the "Boo mouth" picture.
 Super Princess Peach
King Boo aids Bowser in Super Princess Peach. In this game, Bowser's forces capture both Mario and Luigi with some Toads. Although King Boo does not directly watch over Mario or Luigi, he is given a captured Toad to guard, as Mario is Bowser's prisoner while Luigi is Kamek's prisoner.
After adventuring through Vibe Island, Peach discovers where King Boo is and engages him in combat. During the battle, King Boo fires blue homing fireballs at Peach. Peach can damage King Boo with direct light, which is made by having his own flames light the candles spread throughout the room. After a few attacks, King Boo uses his Gloom vibe, which causes him to cry, which extinguishes the candle flames. After enough attacks, King Boo is eventually defeated. With King Boo eliminated, Peach rescues the Toad and continues against Bowser's forces. Ultimately, Peach defeats both Kamek and Bowser and rescues Mario and Luigi.
In this game, King Boo is described and appears as a huge Boo, suggesting that he may not be the same Boo as the original King Boo from Luigi's Mansion.
 Mario Party series
 Mario Party 8
King Boo makes his first appearance in a Mario Party game in Mario Party 8. He gives out Stars on his own course King Boo's Haunted Hideaway. He hides in one out of three altars and gives the player a Star for ten coins if he or she can find him where he is hiding. If the player is able to buy the Star, he will "summon the bizarre" and disappear, causing the player to jump into a Warp Pipe that returns them to the starting point. This "makeover mojo" causes the whole layout of the course to change. However, if they do not have enough coins, King Boo will cause a pitfall to appear under the player, causing them to return to the starting point and allowing the next player that reaches him to buy the Star. Additionally, if the player fails to steal anything from the board event Pickpocket Pinball, the hosting mouse sounds like King Boo. The player can purchase King Boo sounds from the Fun Bazaar, along with a figurine titled "King Boo's Revenge". When the player presses A on the figurine during the Figurine Parade, King Boo floats up and gives off a brilliant glow, as if he is a light bulb.
 Mario Party 9
King Boo appears as the stage boss of the board Boo's Horror Castle in Mario Party 9. He is fought in the minigame, King Boo's Puzzle Attack, where the competitors line up power-ups in lines of three or more to deal damage to him. Once his health reaches halfway, he throws Boos onto the field which can stun the player's cursors, making them unable to move until they shake the Boo off. What is unique about his boss battle is that if a player gets the Final Attack, they get ten points instead of the usual three, likely because the players can easily accumulate points up to fifty. In the final fight against Bowser, King Boo can also appear to hinder the players' progress. If Bowser throws the die with all the stage bosses' faces on it and King Boo's face appears on top, King Boo will materialize above the stage. Then, he will summon five Boos that move in a counterclockwise direction while moving outwards. When the Boos reach the boundaries of the stage, King Boo summons another five Boos, except this time they move clockwise. After that, King Boo disappears from the battle unless his face appears on the top of the die again. King Boo also has a constellation that can be returned to the sky; it is called the Ghost Major. It is located in the farthest left portion of the sky, near Big Bob-omb's constellation and right next to Boo's constellation. Like all constellations, it can be bought for fifty Minigame Points.
 Mario & Sonic series
 Mario & Sonic at the Olympic Winter Games
In the Wii version of Mario & Sonic at the Olympic Winter Games, King Boo appears as the first and sixth (in Individual Festival mode only) rival. King Boo races the player in the Alpine Skiing Downhill event in both Individual and Group Festival modes but he only races the player in Giant Slalom in the Individual Festival mode. King Boo has no skis so he goes down the hill smoothly. If the player loses to him, the guide (either Cream or Toad) says that it is unfair because King Boo has no skis.
In the Adventure Tours mode in the DS version, King Boo is the boss of Polastraits. When the challenger approaches him, King Boo challenges Luigi to an Alpine Skiing Downhill race because Luigi attacked his minions earlier. In this version, King Boo is transparent and the player can ski through him. He also appears slightly larger than in his other appearances.
 Mario & Sonic at the London 2012 Olympic Games
King Boo appears in the next installment of the Mario & Sonic series, Mario and Sonic at the London 2012 Olympic Games. He is one of the characters that can be found in the London Party mode, and when he is encountered, he will challenge the player in the Dream Sprint event. Since he has no feet, though, it is questionable how he gets the ball to roll. If the player reaches the goal line before him, he or she will get a sticker as an award.
 Physical Appearance
King Boo's appearance has changed throughout his video game history. In his debut appearance in Luigi's Mansion, King Boo has dark red eyes, a blue tongue, two vampire-like fangs, a purplish complexion, and a ruby crown. In recent appearances, he resembles a white Boo with a golden crown, though he is noticeably larger. He first appeared in this form in Mario Kart: Double Dash!!, and it remains his current appearance to this day, though his appearance in Luigi's Mansion: Dark Moon shows him with his original appearance, although he still retains a full row of teeth as well as the white color body. He also has his eyes surrounded by a black shadow and has a more purple mouth and tongue.
King Boo is shown to have a deep hatred for Luigi, especially after Luigi defeats him in Luigi's Mansion. He says that he fears nothing except the Poltergust 3000, although in Super Mario 64 DS he admits that Wario's face scares him, rendering the previous statement a generalization. Also, in Mario Super Sluggers, King Boo says that he finds little Boos cute. In Mario & Sonic at the Olympic Winter Games, he says that he is unbeatable at the Alpine Skiing events, though this is proven false when the player beats him. Bowser would sometimes call upon him to aid him in his plans.
 Traits and Abilities
Besides possessing the abilities of other Boos, including the ability to teleport, King Boo has a number of other powers. Notably, King Boo's power increases when he is in the presence of other Boos. For example, King Boo has the power to blow Luigi to the Foyer when enough Boos are in the mansion. King Boo also has the power to materialize things, including highly detailed mansions and lifelike robotic replicas of some of Mario's enemies. He has also shown the ability to create Boos, bubbles, and blue fire, which he spits out of his mouth. King Boo also appears to be a good Alpine Skier, as he states that he is exceptional at that event, though this remains questionable due to his lack of skis.
Although King Boo is much larger than regular Boos, he is not the largest of the Boos. However, even gigantic Boos like Boolossus follow his leadership despite their superior size. King Boo appears with a rather high power stat in many of his spin-off appearances. This is most noticeable in the Mario Baseball series, where he is able to hit home runs with relative ease.
King Boo has an extreme dislike for the Mario Bros., due to their constant intervention in his plans and others of his kind. Lastly, King Boo has a distinct cackle, which is significantly lower in pitch than other Boos.
King Boo is also shown to be able to regenerate from his crown in Super Princess Peach, and in Luigi's Mansion: Dark Moon his new crown exhibits the ability to shoot a laser that can shatter the Dark Moon or trap Toads within paintings.
In "Luigi's Mansion: Dark Moon", King Boo exhibits new abilities, such as being able to open Paranormal Portals and teach Boos how to create Spirit Balls. He can also create illusions, giving him the title "The Master of Illusions." His power is no longer reliant on the presence of Boos.
 Boo Leadership
Although he commands a large band of Boos, not all Boos call King Boo their leader. Some Boos work directly for Bowser, which are most likely the Boo enemies that have appeared in earlier games before King Boo's debut. A small band of Boos are allied with Lady Bow; these ghosts live peacefully with the other denizens of the Mushroom Kingdom (although they still like to scare other species, especially Toads, from time to time). Aside from those other two competing leaders, King Boo controls practically every other Boo in existence.
 Relationships with Other Characters
King Boo and Mario have known each other for a long time. Also, King Boo imprisons Mario in a painting as a consequence for foiling his plans in the past while forcing his brother to explore a haunted mansion to rescue him. Despite their apparent negative relationship, they share a neutral chemistry in the Mario Baseball games. King Boo traps Mario again in Luigi's Mansion: Dark Moon, but his trapping Mario is not his main goal in that game.
King Boo's arch-nemesis is none other than Mario's brother Luigi. When Mario goes to Luigi's new mansion to investigate, he is captured by King Boo. Therefore, Luigi has to go rescue Mario by defeating the Boo leader. King Boo longs for Luigi in the painting too, for Luigi also has past dealings with King Boo. Ever since Luigi's Mansion, the two have shared bad chemistry.
 Petey Piranha
Petey Piranha and King Boo share chemistry in many spin-off games; the two are default partners in Mario Kart: Double Dash!! and they share chemistry in both Mario Superstar Baseball and Mario Super Sluggers. Though the two appear to be friends, their relationship with each other still remains quite a mystery.
King Boo is known to be one of Bowser's right-hand men due to his intelligence and power over Boos. This is shown in Super Mario 64 DS where he guards Luigi's key. Also, King Boo is one of the bosses in Super Princess Peach, so it is likely he is one of Bowser's most important partners for that reason. Also, in Luigi's Mansion, King Boo participates in the final battle in a mechanical Bowser decoy, which he controls. In Mario Party 9, King Boo guards the Mini Stars in Boo's Horror Castle, and can also be summoned by Bowser in the final battle via a roll of the die.
Though no direct interactions have been shown, King Boo and Wario seem to have something to do with each other. In the ending picture to Mario Kart: Double Dash!!, King Boo is shown chasing Wario and Waluigi, scaring the two. Also, in both Mario Baseball installments, King Boo is on Wario's team, though this may not be very reliable since Wario's team may be considered the "misfit team"; there is no noticeable theme through his team (Mario's is Delfino-based, Peach's is Toad-based, DK has characters from the Donkey Kong Series, Yoshi has characters from the Yoshi Series and Bowser has his minions).
 Professor E. Gadd
King Boo originally stated that the only thing that scares him is the Poltergust 3000, which Prof. E. Gadd invented. Also, before the events of Luigi's Mansion, Prof. E. Gadd captures one of King Boo's greatest minions, Boolossus, causing King Boo to plot an attack on Prof. E. Gadd's laboratory and set free all of Gadd's years of ghost-capturing work. This shows that King Boo and Prof. E. Gadd are not on good terms with each other. His hatred towards E. Gadd is stronger in Luigi's Mansion: Dark Moon, as he expressed an interest in trapping E. Gadd within a painting.
 Official Profiles and Statistics
Website Bio: If you're not afraid of ghosts, you will be once King Boo is through with you. To unlock him, finish the Mirror Mode Star Cup with a 1st place win.
Constellation Info: A constellation resembling the king of timid ghosts. Despite his impressive size and cool crown, he doesn't like being looked at.
 Game Appearances
 Names in Other Languages
Note: The Japanese, Dutch and Korean names use the English word for king, instead of a word in their own language.