Back in the days of Mac System 7, there was a boot-screen extension that came up black with a C:\> at the bottom in green. So that had to go on my colleague's Mac IIci, especially since I'd get in early and there weren't locks on his office and no password on his machine.... Then in grad school once, one of my colleagues was using an ORIGINAL Compaq (you know, with the 9-inch screen and the keyboard that doubled as a cover), and since I got in earlier than everyone else, I put a boot program in that started slow-typing the following message several times on the screen: Help me I'm trapped inside your computer The application deleted itself and the screen cleared after a minute or so. I also put one of the lab's stuffed animal mascots into the extra space in the machine. The grad student who turned the machine on was royally surprised....