Mouser is UPL's answer to Nintendo's Donkey Kong. As the cat protagonist, you must rescue your sweetheart from a gang of bad mice. Your girlfriend is held captive on the top of a series of platforms, and before you can reach that platform, you must capture a number of mice, after which a ladder to the top appears. The mice will try to hinder you by throwing items at you; on the first level, they throw flower pots, later on they throw spanners and bombs. Also spread out on the levels are fish, which will speed you up and grant you limited invincibility.