Romeo uses his new invention, the Animal-Metamorpho Ray, to turn Catboy into an actual cat so he can become Robot's pet. He plans to turn all the people in the city into animals for his new zoo. Things get worse when Robot grows so fond of his new pet, that he rebels against Romeo and tries to destroy the invention to ensure Catboy will stay a cat forever. Will Owlette and Gekko be able to change their leader back before it's too late?
The following characters appeared in the episode "Robot's Pet Cat":
Despite Catboy constantly escaping Robot and foiling Romeo's plan by turning off the Animal-Metamorpho Ray to change himself back to normal, he actually thanks Robot for taking care of him, so it may be possible that Catboy secretly liked Robot's company.
This is the third time the PJ Masks say their successful mission phrase in unison.