Baby Billy is Shubie's baby. He makes his first appearance in the episode "Goo Goo Gas." His name is revealed to be Billy in "Free Samples" when his mother, Shubie, tells him to look at Squidward while he is dancing in a monkey costume.
Billy is a light yellow colored fish who wears a spiky purple headgear and a white diaper. He also likes to suck on a pale red pacifier.