Find the "A" key
I think his twin worked for me. Had an engineer who was a slow, two finger typist. He tempted fate by incessantly talking about an upcoming trip to the Caribbean while the rest of us were prepping for some serious cold weather field test action.
Prank? Someone with a pocketknife mirrored the alpha keys on his keyboard: qwertyuiop -> poiuytrewq. When he got back, hilarity ensued.
Prank 2 was filling his cube with balloons, many of which had stink bugs inside, but that's OT