A man walks into a bar with a duck and a biscuit tin. He sets the duck
on top of the biscuit tin on the bar and the duck begins dancing. The
barman finds this rather interesting as do the rest of the punters in
the pub. They all come round the duck and watch it for ages, and while
doing so, buy more and more drink. By the end of the night the bar is
full of people watching this amazing duck, still dancing and giving the
odd quack now and again.
The barman realizes that he hasn't had business this good in a long
time. It is so good that he offers to buy the duck from the man to which
the man agrees to sell for $500. The barman thinks it is a bit expensive
but agrees to buy it anyhow. On selling the duck, the man goes home
leaving a crowded pub watching his dancing duck.
Later that night, the man gets a telephone call. It is the barman and he
exclaims that the duck is a great success and that he has his money back
in the amount of drink he has sold, but he says, "There is one thing...
How do you get the duck to stop dancing?"
The man replies, "Oooh simple! Just take the lid off the biscuit box and
blow out the candle."