Boos typically have white round bodies. Normal Boos have black, soulless eyes, knitted up mouths, small thin hands, and two small sharp points on their bottom which resemble legs. Attack type Boos are larger and have red and orange maniac eyes with black pupils, sharper hands with three pointy fingers and the ends on their bottom have merged into one. Their mouths are also opened, revealing sharp black teeth.
In this game, there are two types of Boo: the ones with black eyes (normal types) and those with red and yellow eyes (attack types). Normal Boos are harmless and scurry along the ground, but will also hide in gravestones, pumpkins, and even just in the ground. When approached, these Boos will pop up in the playable character's face to feign an attack. This does not inflict damage, but can momentarily stun the playable character. After a while, the Boo will disappear, though without earning the player points.
Unlike the normal Boos, attack type Boos can hurt the player like regular enemies. These Boos will float around normally until they spot the player and will start chasing them down. Should they reach the playable character, they will either hold them in place for other enemies to attack them, or attack directly. While just touching an attack type Boo will damage the player, defeating one will earn the player 300 points.
Throwing objects at these enemies will not affect on them, and when defeated in battle, the Boos release neither Animals or Chaos Drives
In Sonic Runners, Boos appear as a Rare Power Type buddy which boosts score for destroying super enemies, and turn enemies into super enemies after reaching certain combo amounts.
During the "Halloween" event, the Boos were being brainwashed by Dr. Eggman who fed them with special candy. A Boo thus aligned itself with Rouge the Bat and E-123 Omega to stop Eggman. When Team Sonic joined the mission, the Boo helped guide the team to Eggman hideout. In the showdown with Eggman and the enslaved King Boom Boo, the Boo then brought Omega a searchlight in accordance to Rouge's orders, which Omega used to restore King Boom Boo to normal.
Similar to their king, the Boos are mischievous and malicious, giggling whenever they cause misdeeds. While normal Boos are rather passive, attack type Boos are much more energetic.
Powers and abilities
The Boos have the ability to levitate and move through midair. As ghosts, they can turn themselves invisible and possess a spirit physiology that causes them to evaporate whenever they take too much damage while tangible.
Boom Boo is large variation of Boos who also first appears in Sonic Adventure 2. Boom Boos look identical to normal Boos, but are able to evaporate three times larger after taking damage or shrink down after being defeated and eventually become attack-type Boos.
In the anime series Sonic X and its comic series published by Archie Comics, the Boos are called Booms. In this media, they are a breed of ghosts from Earth who haunt an ancient castle and the minions of King Boom Boo. They first appeared in "Sonic's Scream Test" where they accidentally released into the living world. However, Sonic and his allies were able to save their victims and reseal them.
The Boos would later return in the Sonic X comics to help King Boom Boo escape into the living world by possessing people. However, they were convinced to return to their eternal resting place.
Before Sonic Adventure 2, there have been similar ghosts enemies called Hyudoros, which act similarly like Boos and are featured inside the pyramid at the second act of Sandopolis Zone in Sonic & Knuckles. Despite these facts, both Boos/Boom Boos and Hyudoros can be consider as separated ghost species.
Boo shares its name with enemies from the Mario series.