Katie first appeared in Animal Crossing: Wild World for the Nintendo DS, and later Animal Crossing: City Folk for the Wii. In both games, she randomly appeared in the player's town. When the player talked to Katie, she asked that they help her find her mother Kaitlin. Kaitlin can be found in another player's town (the friend of the player). When reunited with her mother, the duo will bestow upon the player a random gift.
Super Smash Bros. series
Katie and Kaitlin appeared together as a trophy in the Wii video game Super Smash Bros. Brawl. The trophy appeared randomly in the game. The following is their trophy description:
"A mother and child who've gotten separated. After you've gone to visit a friend's town, you'll find either Kaitlin, the mom, or Katie, the wayward kitten, in your town. Both will tell you where they came from, and it's then your duty to travel to that town to reunite the family. Once you do, the player whose town Katie was in will get a letter of thanks and a present."