Waiter, waiter, will the pancakes be long?
No, sir. Round.
This pun is a play on the adjective "long", which has several different meanings, including:
long (adjective)
1) lasting or taking a great amount of time
2) measuring a great distance from end to end
pancake (noun): a thin, flat cake, usually circular or round in shape
round (adjective): circular, not square or rectangular