King Boo
- This article is about the recurring character introduced in Luigi's Mansion. For the separate character known as "King Boo" in Super Mario Sunshine, see Big Boo (character). For the secret level in Minion Quest: The Search for Bowser, see King of the Boos.
| King Boo | |
|---|---|
 Artwork from Mario Party: Star Rush | |
| Species | Boo |
| First appearance | Luigi's Mansion (2001) |
| Latest appearance | The Super Mario Galaxy Movie (cameo) (2026) |
| Member of | Bowser's Minions |
- “I am not afraid of you, fool! I fear only that infernal Poltergust 3000 you carry on your back! Stupid machine! But I am a KING among Boos! I swear it... I shall fear no mere house-cleaning device!!”
- —King Boo, Luigi's Mansion
King Boo is a character introduced in Luigi's Mansion. He is the arch-nemesis of Luigi and the main antagonist of the Luigi's Mansion series, which also includes him as the leader of the Boos and ghosts. King Boo is allied with Bowser, whom he has assisted on various occasions. He has captured Mario in every game of the Luigi's Mansion series, prompting Luigi to rescue him. King Boo's main powers include materializing objects and spitting fire, though King Boo's power is often directly proportional to the number of Boos in his vicinity.
General information[edit]
Physical description[edit]
King Boo has two distinct designs: one for most of his appearances and the other for the Luigi's Mansion series.
King Boo's common design was first used in Mario Kart: Double Dash!!, where he appears as a large Boo with a golden, five-pointed crown. With this design, the crown has a blue jewel on the front and four red jewels around the sides in every game except Mario Super Sluggers, where the colors are reversed. Like other Boos, King Boo is generally shown with an open, wide grin; however, when looked at, he closes his mouth and bashfully hides his face with his hands. In certain games like Mario Party 9, King Boo's emotions are denoted by an aura surrounding him: when happy, he glows with a blue aura, and when angry, he glows with a red aura. Sometimes he also has steam coming out of him to display his anger. In Dr. Mario World, he has a doctor's mirror on his crown, and he carries a medicine box by a strap. His gold variant in Mario Kart Tour is based on this design and has an entirely golden body similar to a Gold Boo, though his teeth and tongue are golden as well. His crown is silver, and all five jewels are blue.
King Boo has a more unique and sinister look in the Luigi's Mansion series. In his original appearance in Luigi's Mansion, King Boo has dark red eyes, a blue tongue, two vampire-like fangs, a greenish complexion, and a ruby in a gold, round-edged crown. He is also roughly the same size as other Boos. Starting from Luigi's Mansion: Dark Moon, King Boo retains his original appearance but with some modifications: he now has a full row of four teeth, a white body, and a larger size matching those of King Boo's modern Super Mario design. Additionally, he has purple eyes, a dark indigo mouth and tongue, and a purple jewel atop his crown, which has additional pointed edges. He also has a larger shadow surrounding his eyes. In Luigi's Mansion 3, King Boo is shown to be more expressive, often scowling at his allies and enemies and appearing visibly disappointed when captured in the game's credits. His speech icon also uses a green shading reminiscent of his initial appearance, while his portraits show him with a purple crown. In Mario Kart Tour, King Boo's Luigi's Mansion variant uses this design, although his tongue is more purple than indigo.
Personality[edit]
King Boo is a villain who enjoys scaring and tricking his enemies by creating illusions and then overpowering and trapping them. He also admires paintings and other decorations, such as making lengthy comments on how good Mario is as a painting and decorating Treacherous Mansion to be scarier. He is primarily motivated by spite; while his evil schemes often involve amassing power, their end goal is typically to trap Luigi and his allies in paintings as revenge, even in his first appearance. His holding of grudges can also be observed in his dialogue, as he sarcastically refers to his prior defeat in Luigi's Mansion as "good times" and he states that he is "sick to double death" of Luigi.
He takes satisfaction in taunting his enemies, particularly Luigi. In Luigi's Mansion, he insults the Mario brothers for believing mansions get given away in contests; while in Luigi's Mansion 3, he introduces himself with "It's-a me, King Boo!" to mock their Italian accents. In Luigi's Mansion: Dark Moon, King Boo pretends to confuse Luigi and Baby Luigi.
He despises the Poltergust line of devices, often expressing this by loudly mimicking its sound when discussing it. He describes the Poltergust 3000 as the only thing he fears, but also swears not to be afraid of "a mere housecleaning device". In Luigi's Mansion Arcade, he describes the later Poltergust 5000 as a "ratty vacuum cleaner" and a "disgusting machine".
King Boo boasts frequently about himself, relishing in telling Luigi about his escape from E. Gadd's collection and proclaiming the success of his plans early. In Mario & Sonic at the Olympic Winter Games, he also declares himself to be unbeatable in Alpine Skiing GS. However, in Super Mario 64 DS, he admits to being scared of Wario's face; and in Super Mario Bros. Wonder, he hides his face when looked at just as a normal Boo does.
Powers and abilities[edit]
In Luigi's Mansion, King Boo's power increases when he is in the presence of other Boos. For example, King Boo can blow Luigi to the Foyer when enough Boos are in the mansion. King Boo can also materialize things, including pulling a mansion out of the ghost dimension, creating replicas of some of Mario's enemies, other Boos, dimensions to battle in, bubbles, and blue fire (which he spits out of his mouth). King Boo can regenerate from his crown in Super Princess Peach.
In Luigi's Mansion: Dark Moon, King Boo can open paranormal portals to the ghost dimension, create traps such as sand patches, electrify terrain to shock Luigi, use spike balls, grow to large sizes, and teach Boos how to create Spirit Balls. His new crown can also shoot an ectoplasmic laser that can shatter the Dark Moon or trap Toads within paintings. King Boo can create illusions, hence his title "The Master of Illusions." In this game, similar to Luigi's Mansion, his power is stronger when there are other Boos in the vicinity.
In Luigi's Mansion 3, King Boo summons magical paintings to trap people and, to a certain extent, objects inside. He can enlarge portraits in order to capture people as an extension of his paranormal portals. He can also attack Luigi using his tongue, body slams, and spike balls that have bombs in them. He does not need the presence of other Boos to grow stronger in this game.
King Boo has a 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 easily. His great strength is also shown in Luigi's Mansion: Dark Moon, as he summons and makes spike balls fall down simply by slamming the platform.
In Mario & Luigi: Paper Jam, King Boo shapeshifts to trick Mario and Luigi by posing as Paper Mario, and he later briefly transforms into Paper Peach and Paper Bowser. He can also spit blue fireballs and inhale them back in.
Relationships[edit]
Friends[edit]
King Boo has been shown to work with Bowser on numerous occasions, including Super Mario 64 DS, Mario Party 9, and Super Princess Peach. He also used a Bowser decoy, and the two share a portrait after King Boo's defeat in Luigi's Mansion. Despite this, the two share neutral chemistry in Mario Superstar Baseball and Mario Super Sluggers, with King Boo appearing on Wario's team rather than Bowser's. King Boo has also been paired up with Petey Piranha in Mario Kart: Double Dash!!, with the two sharing chemistry in the Mario Baseball games and sharing several statistics in Mario Kart 8 Deluxe as well as the same CPU vehicle parts, with both acting as rivals for each other upon Petey's inclusion through the Booster Course Pass. King Boo also has good chemistry with Wiggler and King K. Rool in Mario Super Sluggers. Luigi's Mansion 3 shows Hellen Gravely admiring King Boo, with her releasing him to impress and aid him in his plot for revenge against Luigi. King Boo pays little consideration toward Hellen Gravely and is more interested in capturing Luigi and E. Gadd, making Hellen Gravely's admiration one-sided.
King Boo relies on his Boo minions, or "friends,"[1] to cooperate with him to try to capture Luigi and his friends. In Mario & Luigi: Paper Jam, he threatens to hurt Paper Mario if the Mario Brothers hurt his Paper Boo minion. He has good chemistry with the playable Boo in the Mario Baseball series. In Mario Super Sluggers, King Boo says that he finds little Boos cute. However, in the later Luigi's Mansion titles, he can be just as cruel to them as he is to his other ghost minions, showing no concern for them being sucked up by Luigi and even actively putting them in harm's way, as well as indirectly calling them useless in Luigi's Mansion 3.
Enemies[edit]
- “You think I'll let you get away with that!? You're going down this time, Green 'Stache!”
- —King Boo, Luigi's Mansion Arcade
King Boo and Luigi are arch-nemeses in the Luigi's Mansion series. King Boo's motivation for trying to imprison Mario and Luigi is revenge for the trouble that both brothers have posed against him in the past. King Boo additionally states that the only thing that scares him is E. Gadd's invention, the Poltergust 3000. King Boo also traps Toads in Luigi's Mansion: Dark Moon and captures Princess Peach in Luigi's Mansion 3. King Boo additionally dislikes Professor E. Gadd for his ghost-capturing hobby, which involving capturing his Boos.
King Boo's rivalry with Luigi can also be seen outside of Luigi's Mansion. In Mario Superstar Baseball, King Boo has negative chemistry with Luigi and Baby Luigi; in Mario Super Sluggers, he additionally has bad chemistry with Mario, Peach, Daisy, Baby Mario, Baby Peach, Baby Daisy, and Yoshi. In the Adventure Tours mode of Mario & Sonic at the Olympic Winter Games on Nintendo DS King Boo selects Luigi to challenge him to Alpine Skiing GS, due to the latter being afraid of ghosts. In Super Mario 64 DS, King Boo was the one to trap Luigi, and Mario must fight him in order to get the key to Luigi. In Mario & Luigi: Paper Jam, King Boo captures Mario and Paper Mario, leading Luigi to search for them.
Generally speaking, King Boo cares nothing for ghosts that are not Boos, considering them expendable to advance his grand schemes, such as in Luigi's Mansion: Dark Moon, where he caused friendly ghosts to turn hostile so he could try to take over the Mushroom Kingdom. Even Hellen Gravely, who has great admiration for King Boo, is seen by him as nothing more than a tool for his plans, and he deems her useless as she fails to capture Luigi.
History[edit]
Luigi's Mansion series[edit]
Luigi's Mansion[edit]
| King Boo | |
|---|---|
| |
| Title | King of Boos (3DS) |
| Age | ??? |
| Room | Roof/Secret Altar |
| HP | 500 |
| Gallery number | 23 |
Prior to the events of Luigi's Mansion and its remake, King Boo somehow freed Boolossus, who had been captured by Professor E. Gadd at some point, and then King Boo ordered the release of every other ghost that E. Gadd had captured.[2] After releasing all the portrait ghosts, King Boo created a haunted mansion near Professor E. Gadd's Lab. Luigi later receives a scam letter, presumably from King Boo, stating that he had won the mansion and plans to celebrate over there with Mario.[3] However, King Boo imprisons Mario inside of a portrait and places him in the Secret Altar.
During gameplay, King Boo is first seen in the Storage Room, where he and the other fifty Boos spring out from the floor after Luigi opens it. When King Boo notices the Poltergust 3000 on Luigi's back, he orders the Boos to stop their surprise attack and retreat.[4] King Boo is located in the Secret Altar in the mansion's basement for the remainder of the game. Aside from the Secret Altar Key, reaching King Boo requires Luigi to have caught at least 40 Boos, or else King Boo blows Luigi to the Foyer. In the Secret Altar, King Boo stares at Mario in the painting while insulting the brothers' intelligence for having fallen for his scheme.[5] 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, which is changed to depict Bowser instead, and he inhales Luigi into the painting. Luigi is transported into an arena modeled after the roof, and this is where the final boss fight occurs. It is actually just a Bowser suit controlled by King Boo during the battle, both to retreat in and for attacking Luigi. Attacks from the Bowser suit include shooting flames at Luigi (dealing 10 HP of damage), throwing Spiked Balls (also dealing 10 HP of damage), or inhaling Luigi and spitting him out, inflicting 15 HP of damage. King Boo emerges from the Bowser suit after Luigi shoots a Spiked Ball at the Bowser suit right before its inhaling attack, blasting off Bowser's head. King Boo has 500 HP, more than any of the other portrait ghosts, and as Luigi depletes King Boo's health, the Bowser suit's head hovers around the arena, shooting icy blasts, which can freeze Luigi on contact. Seconds later, King Boo returns into the dormant Bowser body, and the head reattaches itself. The process repeats throughout the battle, but once King Boo's life falls below 200 HP, the head of the suit reattaches backwards when King Boo returns into the suit, which then runs around aimlessly before properly reorienting his head. When King Boo is vacuumed into the Poltergust 3000, Luigi automatically receives King Boo's crown. Back at the Portrificationizer Chamber, both King Boo and the fake Bowser can be seen in the Ghost Portrificationizer as it presses them and the other portrait ghosts of area 4 back into paintings, marking an end to Luigi's journey. King Boo and the fake Bowser are both included within the same portrait.
Luigi's Mansion: Dark Moon / Luigi's Mansion 2 HD[edit]
King Boo reprises his role as both the main antagonist and final boss of Luigi's Mansion: Dark Moon and its Nintendo Switch port, Luigi's Mansion 2 HD. He escaped some time after Professor E. Gadd had sold the portrait of King Boo from the previous game at a garage sale (a car boot sale in British English versions).[6] King Boo shatters the Dark Moon into six pieces with a bolt of energy from his crown, turning the ghosts of Evershade Valley into hostile, mischievous beings that serve King Boo. Towards the climax of Luigi's journey, in which he recovers the Dark Moon shards from each of the mansions, King Boo is revealed to have trapped Mario in a painting again. King Boo later captures Luigi after he recovers the last Dark Moon piece and pulls him back into his dimension. King Boo makes Luigi realize that he had escaped from the painting and broke the Dark Moon. King Boo intends to use the ghosts as an army to conquer both Evershade Valley and the Mushroom Kingdom while also planning to put Luigi, E. Gadd, and all their friends into paintings for revenge. King Boo then engages in battle with Luigi, where his attacks include summoning a series of magic lightning bolts with his crown and attempting to slam Luigi with his body. The latter causes spiked balls to fall from above, which will roll around the tilting platform to pose a hazard. King Boo will stop moving when looked at, and when caught underneath a falling ball, he will become stunned, leaving him vulnerable to the Poltergust 5000. Once his HP is depleted and he gets sucked into the Poltergust 5000, he immediately breaks out and sends Luigi into a floating hallway. He then swells to a large size and begins rolling after Luigi, attempting to stall Luigi with various obstacles, such as falling shelves and suits of armor with large polearms. If King Boo does hit Luigi, he will pause for a moment to laugh maliciously. Once Luigi makes it out of the hall, he will land on another tilting platform, where King Boo will repeat his previous patterns at a higher intensity. The battle concludes after the third battle and second hallway chase, leading to King Boo being defeated and sucked into the Poltergust 5000.
King Boo's design is derived from Luigi's Mansion, albeit larger and with an additional full set of teeth and a sped-up voice from other games in the Super Mario franchise. Some of King Boo's new features include a purple tongue and mouth and glowing purple eyes.
Luigi's Mansion Arcade[edit]
King Boo is the final boss in Luigi's Mansion Arcade. He leads his ghosts in an uprising to get revenge on Luigi and E. Gadd. King Boo assaults Luigi on the terrace of the Treacherous Mansion after Luigi has sucked in all of his minions with the Poltergust 5000. Protected by a magical barrier, he can only be attacked once he lets his guard down. King Boo throws bombs at the player, moves very quickly, and clones himself multiple times over the course of the fight. However, only the original has the power-enhancing gem on his crown. Just like in Luigi's Mansion: Dark Moon, he escapes the Poltergust 5000 two times before being defeated for good.
Luigi's Mansion 3[edit]
King Boo is the main antagonist and final boss in Luigi's Mansion 3. King Boo utilizes his design from Luigi's Mansion: Dark Moon, but with more detail on his crown and a more expressive scowl. King Boo had been released from Professor E. Gadd's custody by Hellen Gravely, hoping to win his affection. Seeking revenge on Luigi for his previous defeats, King Boo traps E. Gadd, Mario, Princess Peach, and the three Toads in portraits before going after Luigi, who narrowly avoids it by going down a laundry chute. King Boo later entrusts Hellen Gravely with Mario's portrait. It is implied that King Boo planned for Luigi to win both due to Gravely's failures by that time and so he could capture both alongside Peach by using the latter as bait, also recapturing the Toads and E. Gadd just after Mario was freed. King Boo fails to capture Luigi again atop the hotel because the Polterpup shoved Luigi out of the way of King Boo's portrait. Following this is a battle against King Boo, who can take damage from Luigi throwing a bomb from a spiked ball into his mouth and then from having his tongue pulled by Luigi and Gooigi together and being slammed repeatedly. After this, King Boo will generate a clone that attacks alongside him. The clones have only two teeth, like King Boo from Luigi's Mansion. After this is done twice, King Boo will enlarge the painting, and Luigi will then have four minutes to attack King Boo one last time. However, a Gold Bone can reset the timer. The battle ends with King Boo being recaptured by Luigi and placed in a containment jar alongside Gravely, much to his frustration. As the purple gem in his crown was taken by Luigi after the final battle, it is missing from his crown.[7] The Game Over sequence shows King Boo gleefully looking at Luigi and the others trapped in their own portraits.
Super Mario-kun[edit]
King Boo appears in a short chapter on Luigi's Mansion in volume 26 of Super Mario-kun. Luigi reveals King Boo by knocking off the Bowser illusion's head, though King Boo is immediately sucked into the Poltergust 3000, unlike in the games.
Mario Kart series[edit]
Mario Kart: Double Dash!![edit]
King Boo is an unlockable character in Mario Kart: Double Dash!!, his first playable appearance. His default partner is Petey Piranha, and both characters are unlocked simultaneously by placing first in the Star Cup in Mirror Mode. He and Petey Piranha are unique for having the ability to use every other character's Special Item, barring the Green Fireball or Birdo's Egg. 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 on the pipe stood on by the back driver. Additionally, it has a low speed stat and high acceleration stat, in contrast with the other heavyweight karts in the game. King Boo appears to slightly shrink when he becomes the driver. On the second "Thanks for Playing!" screen, King Boo appears in the background chasing Wario and Waluigi.
King Boo is referred to as "Boss Teresa" both internally and for the debug menu in the demos and debug build; this name is used for the Big Boo boss from Super Mario 64 and Super Mario Sunshine outside localized releases, instead of his usual name, "King Teresa".
Mario Kart DS[edit]
King Boo is a boss in Mario Kart DS, where he is fought by Peach on the lava arena at the end of Level 4 in Missions Mode. During the boss fight, he steals at least ten coins from Peach and causes the other coins to disappear. By bumping into him, he turns translucent and reveals the coins he stole. Driving through King Boo while he is in this state lets the player recollect those coins and makes the other coins reappear. He is defeated after collecting all 50 coins.
A variation of the King Boo and Bowser portrait from Luigi's Mansion appears in the titular race course, except King Boo is not depicted in it.
Mario Kart Arcade GP 2[edit]
King Boo makes a cameo in Mario Kart Arcade GP 2. A large picture of him appears near the end of Yoshi Park 2, inhaling many ghosts and the racers to send the latter back to the start.
Mario Kart Wii[edit]
King Boo is an unlockable playable character in Mario Kart Wii. He is billed a large-sized driver. King Boo is unlocked by either completing the Star Cup in 50cc or playing 750 races. King Boo features a good handling bonus and a small off-road bonus. King Boo is one of the few characters whose standing animation on the character select screen has been changed from Mario Kart: Double Dash!!, no longer hanging his tongue out of his mouth prior to being selected. King Boo is the character used by the Staff Ghost on the SNES Ghost Valley 2 course. He is seen during the end credits driving the Jetsetter on said course.
Mario Kart 8 Deluxe[edit]
King Boo is a playable character in Mario Kart 8 Deluxe. He is among the lightest of the five heavyweight groups, sharing his statistics with Rosalina, Link, and Pauline. King Boo has the lowest top speed and weight of all the heavyweights, all while sharing similar acceleration as other heavy groups. Both King Boo's handling and mini-turbo boost are amongst the best of the heavyweights (shared with the metal characters and Petey Piranha). His traction stat is noticeably strong, and it is the highest compared to others in his weight class. King Boo has the third-best base traction stat out of every racer. King Boo's horn sound uses the same sound effect as the Super Mario Sunshine boss of the same name makes when hit by a pepper. King Boo is the 150cc Staff Ghost for GBA Boo Lake and the 200cc Staff Ghost for three courses: Twisted Mansion, GBA Snow Land, and 3DS Rosalina's Ice World. Although without a rival in Grand Prix in the base game, King Boo was uniquely given a rival in Petey Piranha since the fifth wave of the Booster Course Pass, and vice versa.
Mario Kart Arcade GP DX[edit]
King Boo is a playable character in Mario Kart Arcade GP DX. He is a super handling type character, sharing his stats with Baby Mario and Baby Peach. He was originally only playable during a limited-time event campaign held between October 18, 2017, and January 10, 2018, but not in international releases. King Boo could become available even after the event if Bana Passport users collected three in-game stamps, though an update on October 10, 2018, made King Boo available for users who did not participate in the aforementioned event.
Mario Kart Tour[edit]
King Boo is a playable character in Mario Kart Tour. He was introduced in the 2019 Halloween Tour. King Boo is classified as a Super driver, and his special skill is the Lucky Seven. Two variants of King Boo were introduced, including King Boo (Luigi's Mansion), also introduced in the 2019 Halloween Tour, who uses his design from Luigi's Mansion 3. This variant is listed as a High-End character and has the Bob-omb Cannon special skill. King Boo (Gold) was introduced for the 2020 Halloween Tour, sporting a golden body and blue-jeweled silver crown. Also listed as a High-End driver, he uses the Coin Box as his special skill, and, like other metallic characters, a distorting filter is applied to his voice. Unlike most characters, King Boo's head icon is recycled from Mario Kart 8 Deluxe, rather than having a new one that uses his in-game model. Similarly, the head icons for his Luigi's Mansion and gold counterparts also use their in-game artwork.
In pre-release materials, including the beta test, King Boo was classified as a Super Rare (High-End) driver, and his special skill was the Double Bob-ombs, sharing his change in classification between the beta test and final game with Rosalina.
Mario Kart World[edit]
King Boo returns in Mario Kart World. His design in this game resembles his design from Super Mario Bros. Wonder, but with a more pronounced overbite, resembling Boos from earlier Yoshi's Island and Paper Mario games. King Boo can be unlocked by completing the Leaf Cup in any engine class; like the other unlockable characters, he appears as the main rival in that cup if he is not being played as. King Boo is a heavyweight, sharing stats with Conkdor,[8] although the in-game stats screen rounds statistics such that they also match Pauline, Piranha Plant, Snowman, Rosalina, and Cataquack. King Boo has three outfits: Pro Racer, Pirate, and Aristocrat.
Pro Racer
Aristocrat
Pirate
Super Mario series[edit]
Super Mario 64 DS[edit]
King Boo,[9] though erroneously named Big Boo in Western releases,[10] is a boss in Super Mario 64 DS. King Boo is located in a room at the end of Big Boo Battle. The audibility of King Boo's cackling voice is a guide for Mario to navigate his way through several rooms to the end. At the beginning of the fight, King Boo is visible only in the mirror, though his shadow appears in the room. He chases the player and stops only when the player looks directly at him. If he chases the player for long enough, he disappears from the mirror and reappears in the room. While he is in the room, he also chases the player and stops to spit out blue fireballs twice. These fireballs sometimes leave behind coins when they expire. Additionally, his shadow does not appear in the mirror. After spitting out fire twice, he returns to the mirror. King Boo is vulnerable to Pound the Ground attacks, dives, kicks, and punches. After being defeated, King Boo drops the Luigi Key he had been guarding, allowing the player to unlock Luigi's door in the princess's room. King Boo can be fought against optionally by the other player characters except for Yoshi. King Boo's dialogue when encountering Luigi shows him to be confused but deciding to attack Luigi nonetheless. In their initial encounter, King Boo is shown to be alarmed by Wario's appearance.
King Boo and Big Boo use the same model, with a modifier denoting the presence of the crown.
New Super Luigi U / New Super Mario Bros. U Deluxe[edit]
King Boo makes a cameo appearance in New Super Luigi U and New Super Mario Bros. U Deluxe. His art from Luigi's Mansion: Dark Moon is featured as a sign hanging from the side of the building in the secret exit of Vanishing Ghost House.
Super Mario Bros. Wonder / Super Mario Bros. Wonder – Nintendo Switch 2 Edition + Meetup in Bellabel Park[edit]
King Boo is an enemy in Super Mario Bros. Wonder. This is the first game including him as a regular enemy. King Boo chases the player characters while singing with an operatic baritone voice. King Boo covers his face when looked at but continues singing, albeit with a voice distortion filter. When the player characters collect the Wonder Seed, King Boo's crown will fall off as he shrinks into a regular Boo. King Boo appears in Light-Switch Mansion after activating the Wonder Effect "A Night at Boo's Opera." and in The Final Battle! Bowser's Rage Stage upon reaching the jack-o'-lantern pumpkin boxes.[derived] Once players enter the zero-gravity section, King Boo again loses his crown, shrinks into a regular Boo, and floats away off-screen surrounded with music notes.
King Boo reappears in the Nintendo Switch 2 edition of the game with a new appearance in one of the Local Multiplayer Plaza attractions within Bellabel Park known as Think Fast: Boo's Coin Spree. Here, he will periodically appear sleeping in the background, but upon waking up, he can summon Boos that stun players that are still moving when he does so with cobwebs.
King Boo uses different laughs in both of his appearances: in Light-Switch Mansion's Wonder Effect, he uses his high-pitched giggles from his more recent appearances just before he appears, but in Think Fast: Boo's Coin Spree, he instead uses his lower-pitched laughs from his earlier appearances such as Luigi's Mansion and Super Mario 64 DS.
Super Mario Run[edit]
A statue of King Boo in his Luigi's Mansion: Dark Moon design was made available in Kingdom Builder of Super Mario Run during the Luigi's Mansion 2 HD event. It is unlocked by completing six "Luigi's Ghost Hunt" missions.
Super Mario Stadium series[edit]
Mario Superstar Baseball[edit]
King Boo is a default playable character in Mario Superstar Baseball. He is a member of Wario's baseball team, the Wario Greats. Being billed a Power character, King Boo can hit long outfield drives and even home runs. King Boo has good batting, although curved like Boo's, and he has average pitching and fielding and a slow running speed. King Boo's ability is Super Jump, allowing him to catch high balls in the outfield. King Boo shares good chemistry with Boo and Petey Piranha but bad chemistry with Luigi and Baby Luigi. King Boo uses the same baseball bat as Boo, but with a crown on top.
Mario Super Sluggers[edit]
King Boo is a playable character in Mario Super Sluggers. His stats are similar to before, although his pitching is improved and matches his batting power. King Boo's ability is Teleport, allowing him to teleport safely onto the base during close plays if performed correctly. King Boo shares good chemistry with Petey Piranha, Boo, Wiggler, and King K. Rool whilst having bad chemistry with Mario, Luigi, Yoshi, Baby Mario, Baby Luigi, Baby Peach, and Baby Daisy. The baseball bat used by King Boo was redesigned to have a crown emblem above the Boo emblem instead of an actual crown on top. In this game only, the colors of the jewels on King Boo's crown are reversed. In Challenge Mode, King Boo is a member of Wario's team, the Wario Muscles, and appears right after defeating 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 Boos with them, more specifically the Mini Boo item.
Super Princess Peach[edit]
King Boo is a boss in Super Princess Peach. He is encountered in Shriek Mansion 3-6. While going after Princess Peach, King Boo attacks by firing blue homing fireballs. King Boo can be damaged from direct light, which is created by having his own flames light the candles spread throughout the room. After a few attacks, King Boo uses his Gloom vibe to cry and therefore extinguish the candle flames. King Boo is eventually defeated from enough hits, and Peach rescues the Toad he had been guarding.
Mario Party series[edit]
Mario Party 8[edit]
King Boo is a non-playable character in Mario Party 8. He is the proprietor of the board King Boo's Haunted Hideaway. He hides in one out of three altars and gives a Star to whoever can find him in exchange for ten Coins. King Boo returns the player to the starting point from a Warp Pipe through "summoning the bizarre" after they purchase the Star while also altering the layout of the board, which also ejects any other players from the board. If the player does not have enough coins or declines his Star, King Boo causes a pitfall to appear beneath them, returning the player to the starting point without any Star, and he does not shuffle the board. There are purchasable King Boo sounds from the Fun Bazaar, along with a figurine titled "King Boo's Revenge". When the player presses 
on the figurine during the Figurine Parade, King Boo floats upward while glowing. During the board event, Pickpocket Pinball, if the player does not manage to steal anything, the hosting mouse gives off a sound similar to King Boo's.
Mario Party 9[edit]
King Boo is a boss in Mario Party 9. He is encountered at Boo's Horror Castle, being fought in the minigame, King Boo's Puzzle Attack. King Boo takes damage from competitors lining power-up icons in lines of three or more. Upon reaching half damage, King Boo starts throwing Boos onto the field that can stun the player's cursors. In the minigame Bowser's Block Battle, King Boo can materialize above the stage when Bowser throws the die with all the stage bosses' faces on it and if it lands with King Boo's face on top. King Boo summons five Boos that move in a counterclockwise direction while moving outwar