Back around 1990 we had a college lab full of PC XT clones on an early Novell network on 'thinnet' (shared coax cable instead of star topology twisted pair to a switch). Some of the games floating around relied on the original PC's 4.77 MHz clock and ran too quickly on our 'turbo' 10 MHz machines so there was a slowdown utility that generated regular interrupts looping over a NOP to allow the games to run.
I thought it would be a great prank to put this slowdown utility on the boot floppies and AUTOEXEC.BAT of half the machines in the room and watch my classmates scratch their heads over some slow computers. Instead, it messed with the CSMA/CD (collision handling) on the network cards and essentially brought that portion of the network down. I showed up to a very angry network admin who had spent hours troubleshooting network cards and cable before finally finding one of the affected boot floppies. Fortunately (for me) he blamed another group and I escaped the full brunt of his wrath.
Shared medium, wired or wireless, always offers some extra fun.