Mendel, a popular waiter at Yitz's Delicatessen, passes away, and some of his customers decide to go to a spiritualist who says that he can contact Mendel in the afterlife.
"Just knock on the table as you did when he was with you," says the medium, "and he will appear again."
There is much knocking, but no sign of Mendel. The group bangs louder and louder, and finally they begin to call his name, louder and louder. Then, Mendel appears, with a cloth over his arm.
"What happened, Mendel?" says one in the group. "Why didn't you come when we first knocked?"
"It wasn't my table," says Mendel.