Two vampire bats are going for their midnight feed.
After an hour or so, one bat gets tired of looking and goes home with no blood.
The other vampire bat comes home with blood dripping from its mouth. The first vampire bat says enviously, “Where did you get all that blood from?”
The second vampire bat replies, “Follow me. I’ll show you.”
After awhile the second vampire bat leads them to a cave. He says, “You see that wall over there?”
The hungry vampire bat excitedly says, “Yes!”
Other vampire bat says, “I didn’t.”