In junior high, I was learning C and I made a fake DOS prompt that responded to `cd` and `dir` but anything else would just return `Bad command or file name.`
This was back in Windows 95 days.
Anyway, our computer lab was networked, but literally you could write to any C drive on any computer. So for shits and giggles, I copied my fake DOS prompt to every computer, and added it to every `autoexec.bat` so it would run at startup.
Things were cool for a couple of days but over the next few, the started grouping us up on fewer computers because some of them were "having problems." I thought it was funny at first, like I remember nearly suffocating because I was laughing so hard wherever I thought about it. But one of those days, we came in to the computer lab and all of the computers were gone. The teacher said they had a virus somehow, and were getting them fixed. I started to get nervous then.
Well dude, months went by and those computers never came back. Every time someone started talking on the PA, I feared it would be calling me to the principal's office. Or perhaps a letter home to my parents. Holy shit I got paranoid for a12 year old, wondering if people knew what I did but were waiting to fuck me over.
Well, none of that happened. Apparently Gateway said the computers were unrecoverable (lol) and new ones weren't in the budget. We just played heads up 7 up for the rest of the year and we all got A's.