There is a joke that I can't understand. Who can help explain? Today is April Fool's Day. I specially cut a turtle out of paper and stuck it on my back, then turned my back on it.

This is a scam. He put a turtle pattern on his back. When people see it, they will say, there is a turtle behind you. But if you stand in the other person's position, you will think, "Is there a turtle behind me? Isn't that you behind me? " So the man standing behind you is a turtle in disguise, so. . . . . . A cold joke, dear.