Not really MY pet ticking me off...

MY ex roommie had a dang cat that would pee on ANYTHING left on the floor if it was made of fabric...clothes, jackets, hats socks ANYTHING! Urgh. The cat was box trained too. And sometimes, if you had a shirt up on a dresser or hanging on a hanger low enough to get knocked over, she would purposely knock the thing over and pee on it! I had no room with a door so I couldn't keep the cat out....I STILL have to wash cat pee off of some of my stuff! Not to hijack the thread but what causes this? Someone PM me or something cause Im curious....