I found out a while back you could change the ‘ready message’ on an HP printer by telneting to port 9100 of the ip address of the printer and entering the following:
@PJL RDYMSG DISPLAY='Please Insert Coin(s)'
People actually left money on the top of the printer. I’m sure (I hope) they were just playing along, but I got a laugh or two from it. This information can also be changed from the HPJetAdmin software but I found that out later, not everyone has it, and that’s just not as cool. I tried it on a Xerox printer but that just seemed to print out some garbage.