"What the...A ghost?"
~ Knuckles the Echidna's reaction upon encountering King Boom Boo.

King Boom Boo (キングブーブ Kingubūbu?), also known as the "King Of Ghosts", is a minor villain in the video game Sonic Adventure 2 and in the anime Sonic X. He is a giant ghostly beast who rules all a leguion of spectral monsters known as Boom Boos (also called "Boos"). He resides in the Death Chamber level, yet his presence is seen at the giant pillars of the Pumpkin Hill level and Aquatic Mines level, and like other ghosts in the Sonic the Hedgehog universe, he is repelled by light.


Knuckles encounters King Boom Boo while searching for keys to a door Sonic, Tails, and Amy were trying to get through. In the boss battle, Knuckles runs around a circular arena while followed by King Boom Boo who throws blue fireballs at him (and may also attempt to bite him at close range). Occasionally the ghost stops to spew a huge blue wave of flames, and during that time Knuckles must stun King Boom Boo by activating an hourglass which opens panels in the ceiling, making light fill the room. After that you must chase his shadow across the room and dig it up, then run after him and punch him. He can be damaged up to three times in one hourglass flip. If you go too fast when running from him, he will come the other way round.

King Boom Boo has not appeared in any game since Sonic Adventure 2.


King Boom Boo is malicious, sadistic and mischievous, laughing merrily when causing harm to others. However, he also has a cowardly side, as when the odds would turn against him during his battle with Knuckles, he would resort to running away. He also has a great aversion to sunlight and will try to hide from it. He appears incapable of coherent speech, only giving off babbles, grunts and roars.

Appearances in other media

King Boom Boo and the Boom Boos

King Boom Boos and his legions of Boom Boos as seen in Sonic X comicbook series.

King Boom Boo appears alongside his minions in both the anime series Sonic X and the Sonic X comic book series by Archie Comics.

King Boom Boo, along with his Boo/Boom Boo minions also made an appearance in SOnic the Comic Online', where he is only referred to as the "King of Ghosts".



  • King Boom Boo is the only boss in Sonic Adventure 2 to have green text appear on-screen before facing him, most likely because the color looks ghoulish.
  • Although it was never shown, it is possible that Knuckles was afraid of King Boom Boo, as when he notices him, he says "What the... a ghost?!", but he only says it with a little disbelief. However, in an unused line, Knuckles screams "What?! A ghost!" in a more frightened tone, and in the Japanese version, Knuckles says "O-Obake!", meaning "G-Ghost!", and he is clearly very scared, this is funny because Knuckles has always had the tough guy-persona.
  • His presence can be seen at the giant pillars within Pumpkin Hill and in Aquatic Mine.
  • King Boom Boo was suggested as a character for issues of the Sonic Archie Comics following "Sonic the Hedgehog #134", but the plot in which he was intended to feature was cut.
  • King Boom Boo and that of his people are very similar to the Boos from Nintendo's Super Mario Bros. series. His name even contains "Boo" and "King", a similarity shared by King Boo.
    • King Boom Boo actually came BEFORE King Boo who first appeared was in Luigi's Mansion, which was released the same year as, but several months after, Sonic Adventure 2.
    • It is possible that King Boom Boo was based on the boos from Mario.
      • When fighting him, the player can see a picture of a Nintendo Boo and a regular Boom Boo on the wall, giving even more evidence.
  • King Boom Boo and the other ghosts in Death Chamber look similar to Hyudoro in Sandopolis Zone in Sonic & Knuckles. Also, both of them live in pyramids.
  • There is a glitch in the boss fight when the windows on the roof of the arena are opened if the player pauses the game. The sky will change from blue to black. If the player resumes the game, the sky will return to its normal color. However, if the player restarts the game from the pause menu, the sky will stay black for the rest of the fight.
  • Strangely, if the player restarts the battle, there will be a scene where a Boo lifting the Hourglass will appear, which does not appear before.
  • During the Halloween update of Sonic Runners, it is seen that King Boom Boo has been incorrectly spelled as "King Boob Boo". Developers apologized for the issue and stated that they are fixing the issue in the future. Players have received this notification automatically if they have got the Halloween update. The name was most likely translated incorrectly from the character's Japanese name キングブーブ (Kingu Buubu), which the last word in the name reads more similarly to the incorrect word.