What should I do this year?

Okay, so every year in track season I try to do a couple minor pranks, particularly locker related ones.. Well there's this guy on the track team (my friend) who is EXTREMELY fun to mess with. Last year in track he left his bag in an unlocked locker. I knew it would be funny if he came back and saw his stuff wasn't there so I grabbed his bag and put it in a different locker. Then a second time the next week. Sure enough, his reactions when he was searching all the lockers for it were PRICELESS. He was swearing and getting very pissed off as he looked for his bag. He even kicked a locker cuz he was so pissed off. Better yet, he blamed the baseball kids, who we have to share a locker room with.

This year I want to go hardcore with the pranks and get some good reactions out of this guy. Any good ideas that would really get funny reactions out of him?