Skeleton Baby appears in the episode "City of Thieves." He is the son of Skeleton Mom. Big Guy steals Skeleton Baby away from his mother, but then he steals the ruby from Big Guy's tooth and jumps from his arms. He then runs into Mr. Turtle, who steals the ruby away from him.
Skeleton Baby is a bronze-colored baby skeleton. He wears a teal outfit with gray straps going across his chest and forming pants, giving him a half-mummified look. The model sheet shows that Skeleton Baby also has a pink tongue.