I read on line that it is possible to change the LCD display of most printers by simply sending a TCP packet to it. I tried that, and It works.
I have been wondering why printer's manufacturers have not fixed the issue? since it is some sort of security leak.
Thanks for any ideas.

"@PJL ..."-commands to printers) is how they make the LCD to show "Printing job 'word.doc' by user cathy02". But, in their defense, we have to say that most vendors also do include security measures that can make it very difficult for arbitrary users to send a "Kick my lower tray twice" message. It's up to your printer admin to make it more secure. – pipitas Jul 5 '10 at 21:04