Kitty Kat is Felix's love interest.
In her first known appearance, Feline Follies, Kitty was better known as "Miss Kitty White", as a pun of her natural coloration. When she first met Felix (known as Master Tom at the time), it was love at first sight, even though before that day he was what many refer to as a "cat-sanova", and after all his life breaking hearts of other women (in fact, he still chases after any female feline with the supermodel image), Kitty turns the tables on him, as he couldn't help playing lively music for her dancing, dating her several nights in a row when he should be mouse hunting, and even admitting he'd live all nine of his lives for her (in fact, in The Last Life, he wasted eight of them trying to show off).
In the upcoming series to the 21st century, Kitty Kat is rumored to make a comeback, but up until then, aside old comic clippings, Kitty was substituted by other female cats Felix couldn't resist (like Ursula "Candy" Cattail, the red-head secretary) though some say she's playing around with him with an alterego, as the resemblance between her and this New Jersey city-girl, Sheba Beboporeba, is undeniable. (Also, due to her younger-self guessing Baby Felix's "secret", there might be debate over whether or not she knows how to work the magic bag as well as Felix himself, and if she does, could that be why she hasn't been seen in a while?)
Official Website Description
The only thing consistant about her appearance throughout the year is that she is a white cat.
Although she isn't really married to him with a litter of kittens, as her first episode appearance concludes, Kitty believes that she and Felix were meant to be together in said way via destiny (mostly because they've known each other long before they officially met, as shown in the Baby Felix and Friends series... in the first episode of that, Dreaming of Baseball, her adult/future self reminded the Felix we all know that he's been mischievous since he was a baby)! In fact, she tends to clobber Felix with a rolling pin when he fails to live up to her ideal image of a responsible future-husband (shown at least twice, first on "Mr. Do-All or Jack-of-all-Trades", when she catches him cat-napping, calls him a "loafer" and nags at him that he should get busy and make some "jack" [financial increase] out in town. When Felix falls asleep to her nagging, she sends her rolling pin though a garden-hose and it hits him hard on the head, knocking some sense into him. Kitty was about to hit him again at the end of the episode, this time personally, but when Felix shows her his earnings, she drops the rolling pin in surprise and they share a hug. The second time was in "False Vases", when Felix plays the piano at her house, a bit too roughly, and ends up breaking her prized ming-vase as a result. Felix has a thought-vision of Kitty hitting him in the head with the rolling pin, and in panic, goes as far as China to get a replacement before she has time to notice, but when Kitty came home, Felix breaks the replacement vase before her eyes and, before she had a chance to get the rolling pin, he fainted), but more-often than that, she prefers to give him the cold shoulder, knowing his child-like personality.