What was the funniest April Fool's prank you've played on someone/ or been a victim to?!?

In a PE lesson at high school we were all playing netball and in the changing rooms we'd planned to all fall over and not move and lay on the ground when someone shouted a certain word, of course we did this and the teacher had no clue what to do! we all laid on the netball courts for at least 4 minutes whilst she panicked!