Don't Reinvent the Wheel
Senior pranks are nothing new. They’ve been around for generations of high school students, and virtually every variation of every prank has been attempted at one point or another. The reason that some pranks are more popular than others is that those are the ones that work. Think of the history of pranking as a kind of field testing. Borrow what seems to have worked well in the past and then innovate your own personal touch on top of that.