The Kindergartners are making up their own unique group among the students, the kindergarteners live as uncivilized, and even dangerous, little urchins who wear face paint, carry tribal weapons, harass the older children and have even attempted to cannibalistically eat them (as seen in the first and other episodes). Most of them are voiced by Ashley Johnson, Kath Soucie or E.G. Daily. Two kindergartners, however, Hector and Tubby, are on good terms with the main characters of the show.

Hector (voiced by Kath Soucie or E.G. Daily) is a kindergartner who calls Gus "Safety Man" and he admires him. He was part of a group that the kids mentored.

Tubby (voiced by Jason Davis) is a red haired, overweight kindergartner who yet is really fast as shown in the episode "The Kindergarten Derby". He is one of Mikey's best friends. He and Mikey won the derby and Tubby told King Bob to abolish the Kindergarten Derby and he did.

Captain Sticky - Captain Sticky (voiced by Ryan O'Donohue or E.G. Daily) is the king of the kindergartners and has purple around his lips from eating candy and wears a paper crown. T.J. calls him Captain Sticky "for obvious reasons" (he saw Captain Sticky eat candy, then wipe his hand on himself).

Gilbert (voiced by Kath Soucie)is a very fast kindergartener (both in speed and speech), Gilbert is King Bob's pick to win the Kindergarten Derby in the episode "The Kindergarten Derby". He loses the derby to Tubby.

Cindy is a girl with long blonde hair (Voiced by Kath Soucie). In the episode "The Kindergarten Derby", T.J. and his gang (except for Mikey) pick her to win the Kindergarten Derby. She has a tendency to get distracted.