I did that keyboard prank too at work on a tester pc, just swapped m and n and a few others. People were pissed as fuck and they knew it was me.

When I was in vocational school, back then you could flip the display upside down by ctrl alt down (with amd GPUs I think), so in the IT classroom when no one was there, I logged in to every pc and flipped the screens. Next class was canceled because IT was busy and nobody knew how to fix them.