Both Gekko and Owlette have their own pets, but why doesn't Catboy?

I'm pretty sure the reason is that the creators of PJ Masks didn't want the heroes to be too similar. Greg's pet Lionel appers in the transformation cutscene, so petting Lionel like Greg's "thing" he does before he goes out every night, which could be why Lionel is seen as much as he is in the series. Owlette's pet Birdie makes her first and only appearance in the episode "Owlette's Feathered Friend" and is only her pet so kids watching the show learn the importance of taking care of pets. They didn't do this with Gekko so someone on the team could give Owlette pet advice. Back to Catboy, even though there's that cat roaming around the city, and that Catboy seems to like, Catboy doesn't own the cat.

Like I said before, the creators wanted the PJ Masks to differ. Having a pet is Greg's thing. Maybe there'll be an episode where Catboy gets a pet in the future, but for now, Catboy's sticking to drawing!✏️

See ya next chapter, Bye!