After Raphael trips down a crevice on Tokka's shell, he find's Chompy's egg which then hatched. He took the little turtle up the mountain for its safety, and then named him. After a large scale battle between Tokka and the Triceratons, it is revealed that Chompy is the child of Tokka, whom Raphael briefly gave him back to. Later, Chompy snuck on Raphael's shell while Tokka flew into space to battle the Triceratons, only to be blasted by an exploding dwarf star. Raph then officially adopts him.
When Raphael declares that the team must be prepared to even sacrifice their lives to save Earth, Chompy crawls up his shoulder and yelps at him. Raphael then comforts Chompy, telling him not to worry because he isn't going anywhere. Later on, Chompy yelps again when Raphael says that the Fugitoid will come to Earth with them, once more appearing on Raphael's shoulder.
Chompy appears on Raphael's shoulder while he and most of the team are playing Mazes and Mutants. After Ice Cream Kitty makes a move that gives her an advantage, Chompy breathes fire at her, which angers Michelangelo. Shortly after, Raphael makes an advantageous play, causing Chompy to cheer.
Raphael has been taking good care of Chompy, when word comes over the news that Tokka, who survived the supernova that the Turtles presumed killed her, is heading for Earth. Raphael realizes that Tokka is coming to get Chompy back, and despite how much he's bonded with Chompy, he knows that Chompy belongs with his mother. After having to deal with Tokka and the Earth Protection Force as they do battle with each other, Raphael, aided by Donnie in a Kraang Stealth Ship, is able to get up to Tokka's face to show Chompy to her and explain everything. Touched by Raphael caring for Chompy in her absence, Tokka ends her attacks, entrusts Raph with taking care of Chompy from now on, and departs Earth to return to Magdomar without further problems. Raphael is relieved to be granted permission by Tokka to continue caring for Chompy, but knows that once Chompy grows up, he'll have to return to space and rejoin Tokka, but until then, Raphael is more than willing to care for Chompy until that time comes.
Chompy is briefly seen chewing on half eaten slice of pizza on the floor in Donatello's lab, before being carried out of the room by Raphael.
Chompy sat on Slash's shoulder as he and the other turtles' allies attended Splinter's funeral.
Chompy Picasso is capable of biting and breathing fire.
- Chompy Picasso alludes to the character "Snappy Warhol", sidekick of Terrorpin, whom Tokka was based on.