Ok i needa good prank.......?

ok i wanna oull a prank on thi one guy in my cl it need to be clean but funny it doesnt have to be a one day prank ex-glueing a penny to the floor but somthing like telling him i broke my leg then walking on cruches for the rest of the week i also cant buy anything also i only have him for a short 15 min cl so it cant be to long