Jensen get's cursed by a witch and turned into a dog. It was because he slept with her granddaughter trying to hide the fact he was gay or something along those lines. Anyway he will stay as a dog until he learns to really love another person etc.
Jared work's at a pet store or vet's and on the way to work hit's a dog (Jensen) with his bike. He takes Jensen to his work to fix him. Long story short he takes Jensen home.
I also remember Jeffery Dean Morgan worked with Jared and liked him but Jared wasn't interested. I think Jensen/Jeffery didn't get on.
FOUND story in comments!! =4