also what is really fun is to log into the computer remotely through telnet and then run the "play" command to play funny noises through the built-in speaker.
back in the 90s we'd log into each other's workstations and play silly noises to surprise and amuse each other. there was even a script to automate that. and another script to automatically retaliate...
@tubetime We had a lab of Sun workstations (okay, only five of them, but still) at the university when I was a student and I learned you could cat /dev/audio into a file to record audio, and cat the resulting file back into /dev/audio to play it back.
So of course we'd telnet into other workstations to play sounds on them. It got really stupid until someone snitched and /dev/audio was chmod 0600.