画蛇添足
Once upon a time,there was a nobleman who gave some wine to his servants．The wine was not enough for all．The servants finally decided whoever first finished drawing a snake on the ground would get the cup of wine．One of the servants finished drawing first．He took up the cup,and was about to drink the wine,when he thought of adding feet to the snake．He went on drawing．Then another servant finished drawing his snake．He snatched the wine cup and drank up the wine,saying．“It is I who first finished drawing the snake．What you have drawn is not a snake．A snake doesn't have feet．”