I played this one when I was in grade 7 or 8.
We were in the computer labs, and at one point I switched the keyboards around for mine and the person beside me. So she came back, and tried to type into wordpad, and it wasn’t working. She was starting to get frustrated, when I started typing “STOP POUNDING ON ME!!!! IT HURTS!!!!”
Seriously freaked her out. Of course, she brought a teacher over. And I ended up getting in trouble. But it was fun while it lasted.