My favorite cat rescuing game on the PC
Super Granny from Sandlot Games is a series of 2D platform games I really love. You control a granny cartoon-like character, trying to collect various stray cats and lead them to a safe place, while avoiding or fighting (or trapping into holes you dig with your shovel) various vicious opponents. You can play a version of it online in Flash, but I prefer running the downloadable version in fullscreen.
Make sure to also download the free levels available for the most recent Super Granny games (e.g. Super Granny in Paradise, Super Granny 3 and Super Granny 4 all have lots of extra levels there – also note the level editor and community sharing feature the recent Super Granny games include).