A circus owner walked into a bar to see everyone crowded around a table. On the table was an upside down pot and a duck was tap dancing on it. The circus owner was so impressed that he offered to buy the duck from its owner. After some wheeling and dealing, they settled on £10,000 for the duck and the pot.
Three days later the circus owner came back to the barman and shouted "Your duck was a ripoff! I put him on the pot before a whole audience, and he didn't dance a single step!"
"Well?" asked the ducks former owner, "did you remember to light the candle under the pot?"