Q. What did the grape do when it got stepped on?

A. It let out a little wine!

Explanation: Wine is made from grapes.  Traditionally (that is, a long time ago), grapes were “pressed” by stepping them ( did you see the scene in A Walk in the Clouds?) to get the juice out.  “Whine,” which sounds the same as “wine,” means to complain a little bit about something.  A child might whine about having to eat something he or she doesn’t like; you might whine if someone stepped on you, kind of like the grapes in the joke.