In high school I figured out that you could pop open the dial-type locks on the PE lockers with a weight plate (I don't remember how or why I found this out) without damaging them and then lock them back up none the wiser. We were required to wear a plain white tee and red shorts as our PE uniform. If you didn't have them, then it counted as a no-dress and you had to sit out that day and could ultimately fail PE as a result if you accumulated too many.
So our high school weight room was just off our boys' locker room. Under the auspices of using the restroom during my PE class, I would run down to the weight room, grab a 10-lb plate and then head into the boys' locker room and pop open one of my friends' lockers that had PE at a different time. I would then proceed to stretch the hell out of the neck, sleeve holes and bottom of their white tee. Obscenely stretched out. I'd really go to work on that rough rider. So the neck hole would be gigantic and the sleeves and bottom would be super flared out. Then I would put it back in their locker and lock it back up.
They would then have to wear it during their PE class or get a no-dress. No one ever figured out who or how it was being done, but most of my friends who didn't have PE the same time as me had to look like total dumbasses and be uncomfortable on a regular basis during PE as a result. It was really great. I never did it to a non-friend.
Oh and I also used this method to pop off about ten locks from a rival school's boys' locker room during a track meet (they had opened it up for use of the rest rooms; they had a 10-lb plate holding the door open) and then locked all those locks all over one of my friend's track duffle bag. He was totally

when he came back from running the 200 and saw it. He had to use that bag with them on there for the rest of the season until he got a new one the next year. It was also pretty great. Everytime I saw it I laughed so hard. He kind of knew I did it, but couldn't begin to figure out how. He thought I was like some rough ridin' cat burglar who cracked safes by listening to them. So fun.