In the 1990s, a friend gave me a PCL script for HP LaserJet printers, to send a request to any printer, to make it stop printing and display a custom message on the LED.
I'd prank people at a Wall Street bank, getting the printers to say stuff like, "RASPBERRY JAM", "GAME OVER", "HI SCORE", or "ADD CHEESE".
Overheard the SysAdmin, a rather serious man, on the phone with HP tech support, describing the issue: "Yeah....yeah....ADD CHEESE.....that's the error."
