|King Boo did not originate from fanon, and more information can be found on their respective wiki(s). You may read more about it on the following wiki(s):|
|Full Name||King Boo|
|Family and Relations|
|Main Weapon(s)||His tongue, his Shadow Crown, illusionary magic.|
King Boo is the king of the Boo's, and Luigi's arch nemesis. He despises the Mario Bros., but hates Luigi more. This hatred is more vicious than Bowser and Mario's rivalry. King Boo has great Magical Powers, and becomes stronger if there are more Boos in the area. King Boo is allied with the King of the Koopas, Bowser, and is best friends with Petey Piranha. Also note that King Boo's ambitions to take over Sarasaland are similar to Bowser's ambitions towards the Mushroom Kingdom. He stars in the McBoo series and plays in the Fantendo Football League. Since appearing in the 2001 GameCube launch title Luigi's Mansion he has become a recurring character in several Mario spin-off titles.
King Boo appears late in the game, taking Princess Daisy, Princess Eclair, and the Chestnut King at the wedding of Eclair and the Chestnut King. He tries to get the Marvellous Compass and Star Sprites, but fails to. In the end, he uses the three members of Royalty to boost his power with a special machine. He later gets the Compass and Star Sprites, and supercharges his machine, becoming Lord Fear.
King Boo will appear as the main antagonist in Luigi Vs King Boo: Quest for the Princess. Here, he kidnaps Princess Daisy in an effort to conquer Sarasaland, and Luigi comes to rescue her. Nothing much else has been confirmed, however.
King Boo is a player on the Bowser Villains team on the multiplayer wii sports game Mario Rugby League. He is a skillful player with average strength and speed. His special skill is to phase through players to avoid tackling.
King Boo makes his debut in the Mario Singalong! Series in Mario Singalong Rocks! to unlock him you have to complete Story Mode twice and sing The Animals House of the Rising Sun in Karoke Mode at least once. King Boo reappears in Mario Singalong Down Under! as a default character. To unlock him in Mario Singalong Legends! you have to sing "Every Breath You Take" by The Police in Karoke mode at least once and complete Story mode twice.
King Boo appear as a half main, half minor character in the McBoo's Mansion series. He is the leader of the Boo Troop and McBoo & co's boss. He was weakened and was wounded at his ego by the events of Luigi's Mansion, making him very short-tempered.
King Boo is set is appear in The Dr. vs. Dr. Saga: It all Begins as a minor antagonist.
King Boo appears in the story mode with a mid minor, mid major role. At World 5, Kirby and his new ally, Lavora hops onto Daisy's Cruiser after winning in Cheep Cheep Cheep Islands. King Boo races Kirby on the cruiser. In the end, Kirby wins and he and Lavora went on to World 6. Meanwhile, King Boo met another Kirby character. This time it was King Dedede! He asks where Kirby was and King Boo said that he beat him hours ago. That made Dedede mad!
King Boo returns in Goomsday Wii as one of the bosses controlled by Goomboss. It is he who raises the souls of dead Goombas to create Terekuribos. He is found in the Super Castle named Misery Mansion, surrounded by an army of Boos and Baby Boos. The only way to defeat him is to drink from the Fountain of Death in his battle. This will turn you into a Boo, allowing you to damage the King. He must be attacked three times to be destroyed. The next boss is Petey Piranha.
King Boo appears as a playable character in Mario Kart 8 Wii U. His special move is Bomb Boo.
King Boo appears as a playable character in Mario Kart Wii 2.0.
King Boo appears as an unlockable character with his own course, King Boo Krypt.
- See: King Alastor Boo
King Boo appears in Super Luigi as the main antagonist. His real name here is revealed to be Alastor.
In New! Super Mario Bros. 3D, King Boo appears as the boss of Spooky Ghost Hills.
King Boo appears as the main antagonist and final boss of Super Waluigi!. He steals a legendary treasure from Waluigi and uses it for his own evil purposes. As the final boss, he appears both as his regular form and a new form. When in his first form, he uses his screams, crown, and tongue to attack. If you ground pound his tongue 3 times, he burps up the crown, but then falls on it.
The second phase is harder. King Boo, with the power of the crown, is now part of the Moon. In this form, he can shoots beams of lasers at you, uses his tongue to smash things, and even spits up smaller Boo's. You have to ground pound his tongue 5 times. If you do, he shrinks back into King Boo, and disappears, leaving the crown for you.
King Boo has been confirmed to be an unlockable heavyweight character in Mario Kart Burst. He is unlocked by winning lighting cup on 100cc.
King Boo appears in Captain Toad: Pokémon Trainer as a member of Royal 4 (the game's Elite 4). He specializes in Ghost and Dark type Pokémon. He can be challenged for the fisrt time after defeating the Team Shell. His room is located at Peach's Castle's secret tower, between Lady Rosalina's room and The Big Door.
King Boo was first mentioned by Mario in the fifth chapter as the latter was consoling Luigi after his lost to Bowser two chapters prior. It wasn't until the eighth chapter that King Boo made an actual appearance. In that chapter, King Boo and his underlings showed up at Ludwig's horror castle as Luigi/Mr. L, Lady Bow, Vivian, Doopliss, Mimi, and Nastasia were in the process of searching for one of the eight Purity Stars.
Upon hearing Mr. L boast that he wasn't afraid of ghosts, King Boo immediately recognized his voice as Luigi's, and showed up to confront him. Much to King Boo's annoyance, Mr. L stated that he had no recollection of him. Shortly afterwards, King Boo tried to coax Bow, Vivian, and Doopliss into joining him and the other Boos, claiming that Luigi "takes sheer pleasure and delight in stripping ghosts of their freedom". Unfazed by King Boo's manipulation attempt, the three of them turned down his offer. Shortly afterwards, King Boo ordered his army to attack the heroes. After Doopliss had all of the Boos transformed into pigs (with the exception of King Boo's newest recruit, Shade, who left the area minutes prior to the battle), King Boo decided to have him sealed behind a painting in order for his powers to wear off. He then did the same to Nastasia for a similar reason, figuring that he and the other Boos would have a better advantage if Luigi were to be transformed back into his original, "cowardly" self.
Once the Boos were changed back to normal, King Boo decided to merge with all of them and became King Boolossus. Although Luigi and the remaining heroes tried fighting him off, King Boolossus, due to his immortality, continued to recover from any and all damage that was inflicted upon him. As such, they had no choice but to flee, with King Boolossus promptly giving chase. After they reach a dead end, King Boolossus held Luigi, Bow, Vivian, and Mimi down with telekinesis, materialized, and merged the picture frames that he intended to trap them in. Just as he was in the process of doing so, Professor E. Gadd used the Pixelator to warp the Poltergust 5000 into the room, breaking King Boolossus's concentration. Not wanting to get sucked up again, King Boolossus tried to flee, but Luigi managed to keep him from doing so by snagging him just in time before he flew through the wall, effectively putting an end to the deranged ghostly king's ambitions once again.
Just as Professor E. Gadd pixelated himself into the area to congratulate Luigi and company in person, he revealed that Shade, of all people, was the one who informed him about their dire situation. After Doopliss and Nastasia were changed back to normal, E. Gadd decided to bring the Poltergust 5000 back to his laboratory in order to run King Boolossus through the Ghost Portrificationizer. After Luigi and company were finished defeating Ludwig and retrieving the Purity Star that he had in his possession, they all went to E. Gadd's laboratory, where a surprise birthday party for Luigi (and by extension, Mario) was being held.
King Boo appears in Mario Hoops 3-On-3 Switch (mainly known as Mario Hoops 3-On-3 Deluxe) as a playable character. He is a Tricky character type and his special move is Painting Shot. He is a starter character. His default partner is Boo. His team name is the King Boo Kings
- King Boo is not married to Queen Boo, their naming is pure coincidence.
- King Boo can obtain the King Boom Boo form without the four Gold Boos, although it will be weaker.