King Boom Boo is a colossal spirit, being several times the size of the Boos. His overall appearance resembles that of the stereotypical ghost, possessing a white body with a sack-like shape and pointy turf on top of his head. Dominating his face is a large maw with blue lips, sharp white teeth, and a multicolored tongue. His eyes are also multicolored, but small and swollen with black pupils. Also, instead of legs, King Boom Boo has a wispy tail. He also has two arms with three claw-shaped fingers on his hands.
Sonic Adventure 2
At some point, King Boom Boo took residence in Dr. Eggman's pyramid base. While Knuckles the Echidna was searching for keys to the base's center, King Boom Boo attacked the echidna. With Knuckles using sunlight against the ghost though, King Boom Boo was defeated and dispersed into thin air.
Other game appearances
Sonic Rivals 2
In Sonic Rivals 2, King Boom Boo appears as a collectible card. It can be unlocked by winning the Tails Cup in Single Player mode. The card unlocks Tails' Captain suit.
In Sonic Runners, King Boom Boo appears as a S Rare Fly Type buddy which gives the player a thirty percent chances of having their score boosted when defeating enemies.
During the "Halloween" event, King Boom Boo was released by Dr. Eggman and fed some strange candy which brainwashed him into serving as Eggman's protector of his lastest theme park project. Though King Boom Boo easily got rid of Team Sonic when they intervened, they returned with E-123 Omega whose searchlight could restore King Boom Boo to normal. Though King Boom Boo destroyed Omega's first searchlight, he was restored to normal by a spare. Wanting revenge, King Boom Boo proceeded to chase after Eggman.
Team Sonic Racing
In Team Sonic Racing, King Boom Boo appears in the background of Boo's House. He first appears at the beginning of the entrance into the track's desert temple, where he encouraging the player to enter. Later, he is seen flying past some pillars while watching the passing player. He also appears in one of the final rooms near the end of the track. Here, he floats In midair while making an ominous cackle. During the track's last lap, he arrives at the portal leading out of the desert temple and encourages the player to go through it.
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 greatly hates sunlight and will try to hide from it. He appears incapable of coherent speech, only giving off babbles, grunts and roars.
Powers and abilities
As a ghost, King Boom Boo has several supernatural powers. He is capable of levitation and can move with enough speed to keep up with Knuckles. He also possesses pyrokinetic abilities that enable him to either form blue fireballs and throw them like projectiles or blow blue flames from his mouth. He can as well transform into a dark shadow of himself which can move across any surface, though he can be removed from said surface by force which will make him revert back to his normal form. He can also seemingly turn himself invisible. He possesses as well a spirit physiology that causes him to evaporate whenever he takes too much damage while tangible.
King Boom Boo's strength is tied to the light; when in contact with darkness and shadows, his powers are at their peak, allowing him to become bigger, stronger and invulnerable. Oppositely, he is weakened when in contact with sunlight, making him shrink and vulnerable.
King Boom Boo is encountered and fought by Knuckles the Echidna after clearing through Death Chamber. The fight takes place on a circular platform surrounding a large pillar
To begin with, King Boom Boo chases Knuckles around the arena. If the player gets too much in front of him, King Boom Boo will turn around and chase after Knuckles from the other direction of the area. During the chase after Knuckles, King Boom Boo will throw blue fireballs at him all the while. After a while, he will pause to fire a jet of flame from his mouth: get behind him at this point to quickly to see a smaller Boo carrying an Hourglass. Hit the Boo and he drops the hourglass, opening up a hatch at the top of the temple. When sunshine pours in, King Boom Boo shrinks down to a shadow and tries to escape along the surface of the platform, including the walls and the ground: stand on top of his shadow to hold him in place, then use dig to chase a weakened King Boom Boo out of the ground. As King Boom Boo then flees around the place, catch up to him and attack with the Punch Attack to deal damage. Act with haste however, because when the ceiling hatch closes, King Boom Boo regains his strength. However, if the player can get next to him after a punch, they can hit a second time before the window closes.
Repeat this strategy, although, after each hit, King Boom Boo becomes faster and the sand in the Hourglass runs quicker. Land four hits to defeat King Boom Boo.
King Boom Boo also made an appearance in the Sonic X anime series and its comic series published by Archie Comics. In this continuity, he and his minions of Boos haunt an ancient castle on Earth. He first appeared "Sonic's Scream Test", where he and his Booms tricked Sonic's allies into releasing King Boom Boo into the living world after kidnapping their friends. However, King Boom Boo was shortly after stopped and returned to his world.
In Sonic X #14, King Boom Boo returned to possess enough people to let him enter the living world, but was convinced by Chris and Cream to return to his eternal sleep.
King Boom Boo was suggested as a new character for issues of the Archie Comics following Sonic the Hedgehog #134, but the plot line in which he was intended to feature appears to have been cut.
King Boom Boo is the only boss inSonic Adventure 2to have green text appear on-screen before facing him.
Although it's never shown, it's arguable 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 shock and disbelief. However, in an unused line, Knuckles says "What?! A ghost!" in a more frightened tone, and in the Japanese version, Knuckles says "O-Obake!", meaning "G-Ghost!", and he is clearly scared.
When fighting him, the player can see a picture of a Nintendo Boo and a regular Boom Boo on the wall.
There is a glitch in the boss battle, when the windows on the roof of Boom Boo's 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, a scene features a Boo lifting the Hourglass will appear, which does not appear before.
During the Halloween update of Sonic Runners, it is noticeable that King Boom Boo had been incorrectly named as "King Boob Boo". Developers apologized for the issue and fixed this. Players received this notification automatically, if they had the Halloween update. The name was probably translated incorrectly from the character's Japanese name キングブーブ (Kingu Buubu,キングブーブ?), which the last word in the name reads more similarly to the incorrect word.