Best one I got away with was in high school, the computer science class (FORTRAN on Apple II's) teacher annoyed me - mainly because I learned disk file I/O and taught it to her one morning and that day in class I was working on something else while she lectured and she dared call me out for not paying attention. Pay attention to her regurgitate what I had just taught her that morning? Ah if only I wasn't the shy quiet nerd back then. Anyway, a couple of days later we are working on programs so I took one of my floppies and carefully opened the shell and removed the disk and put it back in the drive. Naturally this cause an error when trying to access it. So I called her over, said I was having a problem she tries the same program, same error. Opens the drive, slides the disk out, LOOKS AT IT, puts it back in, retries the operation a few times. Finally opens the drive and takes out the disk again and suddenly it dawns on her that something is not right.
The best one I THOUGHT I got away with - a group of us in college wrote up a parody song referencing out one EE prof. We had this all figured out - we knew he hung around with another of our professors, so we wrote an anonymous not including the song and our proposal to distribute it in class, and left it in Professor 2's mailbox with the instructions to just say yes or no at the end of class to indicate if he thought Professor 1 would take it in the spirit of humor we intended or if he would be offended, and if he would be offended we wouldn't proceed. A week or so went by and we were getting worried that maybe we were found out or worse, when finally at the end of class one day, Prof 2 said "Oh, one more thing. A week or so ago I got a strange message in my mailbox, I just want to say, I think it's OK." So we went about getting a few hundred copies printed up, and recruited a freshman from our dorm to bring it in - Prof 1 was in the habit of having one of his TAs some by prior to the start time and put a pie of handouts on the front table and we were expected to pick one up on the way in if we saw them. So this freshman brings the stack in and people start taking them, there's a general buzz about the room, and the Prof 1 walks in, sees this (now smaller) stack of papers knowing he had no handout that day, picks one up, glances at it, and shoves it in his briefcase. Not one word, the expression on his face didn't even change. We thought this time we really were in serious trouble, but not one word was said. Ever. This guy happened to be imo the best professor in the EE department so I made it a point to take as many of his classes as I could. Fast forward to senior year, finals are over and I happened to be in the department looking at job notices and he's going to his office as I walk down the hall so he calls me in, mostly to talk about what I thought of the department and my 4 years there, etc. After chatting for a while, we're wrapping it up and he happens to mention this song parody - and says he knew it was us all along!
I did hear that at least for a few years after we graduated, the song was still being distributed. Perhaps the closest thing to a legacy I have at that school.