There's "practical joke" and then there's "being a frelling jerk who's likely to get the dren pounded out of them".

A couple of jobs back I set up something kinda similar which set the LCD job status line on the HP printers throughout the company to randomly display humorous messages and the company's stock price. But that didn't get anyone up at 0-dark-thirty and it didn't interfere with anyone's job responsibilities.

Well . . . I did finally shut it off after the IT people got tired of having to deal with people from the marketing department (and this is absolutely true :) calling that the printer "wasn't working" because PAPER TOO SPICY, or that the printer was experiencing a GRAPE JAM.