He always wants to win, whatever the means and is even willing to cheat to do so. His inflated ego and overall foul attitude attract negative attention from the others. He especially enjoys torturing Quack Quack the indestructible duck, which upsets Kaeloo and is the usual cause of her transformation into Bad Kaeloo.
Mr Cat was bullied by his brothers as a little kitten. When he was old enough he ran away from home, to Smileyland, where he expected peace and quiet, but instead got Kaeloo, Stumpy and Quack Quack.
It is hinted in the episode "Let's Play Goodbye, Mr. Cat!" that he was the last one to get to Smileyland, seeing as he knew the least about the planet's rules. It was also hinted at that he is the oldest of the buddies, however this theory is a little dodgy, seeing as the show suffered from a little continuity, since Kaeloo said that teenagers are not allowed in Smileyland, but she herself is a frog, not a tadpole, and Mr Cat's voice is deep enough even for grown men standards.
Despite, or perhaps because of, Kaeloo's transformations into Bad Kaeloo, Mr Cat seems to have formed a crush on her.
Mr Cat is one of the main reasons the show has one of the things it is known for, it's ability to get mature content under the radar. This mostly consist of the things Mr Cat does to Kaeloo. One example being in Let's Play House when Mr Cat does the unthinkable for a G / PG rated kid's cartoon. (The episode in question actually being G)
Most of Mr. Cat's villainous acts involve torturing Quack Quack, an indestructible duck, with various weapons such as bazookas and chainsaws, despite Quack Quack never having done anything to him. He also bullies the rest of the cast members even though they are supposed to be his best friends and is ungrateful to them when they help him. He is also not above manipulating people to get what he wants, as shown in one episode where he tricks Quack Quack into believing that his girlfriend cheated on him as part of an elaborate scheme to get Kaeloo to kiss him (the scheme ultimately failed). Many of these actions are motivated by his crush on Kaeloo, which often leads to more inappropriate/illegal behavior such as breaking into her house and trying to sleep in her bed.
- Mr. Cat is the show's second most popular character (the first being Stumpy).
- He frequently breaks the fourth wall by speaking directly to the audience.