Wooonderful BDE

A man serving a long sentence fills his time watching and feeding a mouse that has nested in his cell - he becomes intrigued with its behavior so he sets about training it to do tricks
He teaches it to walk on its hind legs, to somersault and eventually, to dance to tunes he whistles
When he is finally released, he manages to slip it into his pocket, intending to make his fortune from it
He heads for the nearest bar hoping to earn a free pint with it - he calls the barman over, places it on the counter and sets it off dancing
The barman stares at it for a minute, reaches for a tray and squashes it flat saying, "this place is crawling with the dirty little fuckers"
Jim Carroll