Another thing I always had fun with was to catch a cricket in a jar. Put a few holes in the lid so it wont die and put it under your buddies bed. You can hide it real good, better if there is a bunch of stuff under there already.
About 1:00 AM he will wake to a sweet symphony........
at 1:10 he will have had enough
at 1:15 the lights will be on
at 1:20 he will find the jar and know hes been had
at 1:25 cricket goes outside
at 1:30 hes back in bed
at 1:45 still awake mad that he was had and there is nothing he can do about it, because he isnt positive who it was that dropped a cricket bomb on him.
the next day......priceless!