Looking for a music video - please help?

I'm looking for a song, which I cannot remember anything about except I heard it years ago and the video is animated, with a grey boy who runs into a toilet cubicle to avoid people staring at him. A black cat gives him some clothes, and he starts writing lyrics on the walls. It was played on Two Pints of Lager and a Packet of Crisps in one episode, if that helps in the slightest. :D Please help! I've been searching for this for years! Thankyou ~<3