I was generally a good kid in high school. My friends were as well. The tradition was that seniors would play some kind of prank, and we absolutely weren't going to miss out on that, but we also wanted to do something that was funny rather than mean or messy. I don't remember who came up with the idea of pranking the school librarians (who were rather unnecessarily draconian and were really asking for it!) but we soon hatched a plan.
One weekend evening, we stopped by one of the night markets (this was in Hong Kong) on the way back from a movie and purchased ten or so inexpensive battery-powered alarm clocks. We synchronized them, turned up the alarm volume as high as it would go, and then set the alarms to go off at five-minute intervals. The next school day, each of us casually wandered into the library sometime during the morning with a set clock or two and hid them. That afternoon, when the library was packed, we casually wandered back in and sat down at a table to "study" and view the effects of our handiwork.
The reaction was priceless. The librarians had a flaming hissy fit, and everyone else in the library thought it was hilarious. No sooner would they find and deactivate one alarm clock than the next would start ringing. And I have to say that some of my co-conspirators were really inspired in their clock placement...one actually managed to get a clock into the librarians' desk itself, and another (I have no idea how to this day) one into the metal ductwork in the ceiling!! That particular alarm echoed throughout the whole library...absolutely brilliant work.
As far as I know, nobody ever connected the group of us to that stunt...this may be the first public admission of guilt. Fortunately, whatever the statute of limitations might be, I'm sure it is long expired. But I'll bet Mrs. Newman is still holding a grudge!