What is a good joke to play on someone?

Here's a simple but effective prank you can pull on someone:

Knock, Knock, Knock It Out

Items needed:

- Piece of string or thread

Instructions:

1. Tie one end of the thread to the doorknob of the chosen person's door.

2. Thread the other end of the thread through the mail slot of the same door.

3. Ring the doorbell or knock on the door and wait for the reaction.

4. When the person answers the door, let go of the thread and quickly hide.

5. Observe their confusion as they try to understand where the knocking or doorbell sound is coming from.