This existed for PCs, too. It was called "drip". When idle, individual characters would "drip" down your screen like raindrops, at random times, for random distances.
Another one I remember was "drain". In the very early PC days, you could add this program to the AUTOEXEC.BAT of an unsuspecting victim's computer, so that it would run at startup. It would start flashing "SYSTEM ERROR 0304-B" for a moment, then add "Water detected in disk drive A:". Another moment, then "Now draining", and it would play this gurgling sound out of the speakers (as best you could, on the speakers of the original PC). That would peter out, then "Now starting spin dry cycle", and it would play this whining sound for a bit, ramp that down, and then tell you that it was OK to use the system now.
In those days, there weren't "logins" to PCs. If you saw a PC without the normal user present, you could do anything to it.