Q: Why didn’t the skeleton go to the ball?
A: He had no body to dance with!

Explanation: “Ball” is a synonym for “dance.”  So, why didn’t the skeleton go to the dance?  Well, because a skeleton is all bones and nothing else, a skeleton does not have a body.  That is, he has no body.  When you put those two words together you get “nobody.”  This joke is funny because it plays with the words “no body” and “nobody.”  If he had nobody to go to the dance with he would go alone.  In this case he had “no body.”