Dunno what made me think of this just now. When I worked for IT in a school district way back in the 90s, a librarian told me she kept a supply of mouse balls in her desk because kids would steal them out of the school computers. What I remember about those balls was they picked up dust and crud off surfaces. Pretty soon optical mice came along and they were history.
Out go to prank was a shut down bat file, disguised as GTA.exe. We used to put that in a shared folder and waited for other students to shut down their computers.
Ha, these were early Macs (right at the launch of System 7) there was only a few kids with these at home so I had a pretty good idea who was brining in the icons and sound files (aiff if I recall correctly). We had one at my home too btw. They were interesting computers but besides shareware and a couple game companies, they were abysmal for games. We did get a copy of Warcraft 1 and could play it over 14.4k directly dialed to the other computer lines with PC users.