A man goes into a pub with a duck and a biscuit tin. He asks the landlord if he can show off his dancing duck to earn some beer and the landlord agrees.
He puts the tin on the bar and the duck on the tin and starts playing his mouth organ. The duck starts tap dancing on the top of the tin!
Word of this gets round and people are flocking in to see the dancing duck. The landlord offers big money to buy the duck off the guy, so money and duck change hands.
Next time the bloke goes into the pub, the barman complains that he's been robbed because the duck won't dance. "Maybe I'm playing the wrong tune", he says. To demonstrate this, he puts the tin on the bar, the duck on the tin, plays a tune but the duck just stands there.
The bloke says to him, "You daft pillock, you've got to light the candles inside the tin first!"