Mr. Cat tells Kaeloo that he and she were "made for each other". The pilot shows that Mr. Cat's antics, which are a crucial part of the show, are motivated by his crush on Kaeloo. And the characters are aware that they live in a cartoon. In other words, Kaeloo and Mr. Cat were literally made for each other.
Mr. Cat's stories about his brothers and dad seem to be consistent, but his description of his mother varies between episodes. In this episode, he mentions that he was adopted by a salmon who raised him as her own son. Depending on the episode, he may be talking about his biological mom or his adoptive one.
Neither cats nor frogs produce one baby at a time.
This episode has a scene where Mr. Cat attempts to force himself on Kaeloo. It takes place after "Let's Play Peace, Man", where Kaeloo forced multiple kisses on Mr. Cat.
Mr. Cat thinks that the best way to get children to listen to you is to beat them into submission. Given his backstory...
The plot of the episode becomes this when you realize that Mr. Cat has romantic feelings for Kaeloo, but she just wants a chance to get pregnant.
If things went according to plan, Kaeloo, a preteen, would have slept with Mr. Cat, another preteen.
Even worse, if Kaeloo had actually gotten pregnant, the end result would be a pair of preteens raising children.
If Kaeloo and Mr. Cat did have kids, those poor kids would have wound up with a mother who turned into a monster and did things she couldn't control whenever she got angry, and a psychopathic and evil father.
The possibility that Mr. Cat was the result of an unwanted pregnancy gives a much darker meaning to the scene in the expository comics where Mr. Cat plays with explosives as a baby.
