I created a directory with alt+255. It was an unprintable character and showed up last in any dir listing. At most it added an extra new line. That’s how I was one of the only students whose apps didn’t get caught during auditing.
However it turned out that you could rename them .bat or .cmd and they would execute just fine.
I think Doom 2 multiplayer was extra fun because of the added need to be aware not just of in-game enemies but also the need to be aware of the teacher and be ready to instantly quit at any moment.