I had seen Timmy a few times in my travels but never realized what a rare spawn he is. Apparently he's one of Stormwind's secrets. I first learned this while watching G4TV when they did a special about World of Warcraft. Since then I never saw him. Until yesterday:
I was able to buy his white kitten for 60 Silver. Apparently you can sell them for 5 gold on the auction house. I think I'll keep this one though.
This Allakhazam.com link includes a picture of his route, although I liked this one better from RPG expert. It also showed his spawn point.