One Tooth

Blind Bat
Blind Bat is an alternate version of One Tooth that starts out asleep. When Isaac gets close, it wakes up and chases Isaac, followed by a group of three more Blind Bats. Blind Bats will also wake up if a loud sound happens in the room, such as an explosion or a Quakey performing his ground smash attack.

Echo Bat
Echo Bat is an alternate version of One Tooth that flies towards Isaac and periodically fires three white orbs. If an orb hits Isaac, he becomes confused and his movement is reversed for a few seconds.

Trivia

 * Blind Bats appear to be based off of Battons from the Mega Man series, as both start invulnerable and hanging from a ceiling with their wings closed and wake up, moving towards the player when they move close to their hanging positions.