It was a server running on each of the four public-use computers in a student study-area/lounge. What the server did was wait for a connection, recieve data, and create a dialog based on that data.
So for instance, people were browsing the interenet, and I would connect to their computer through the local network, and tell it to display a dialog with something like "Are you sure you want to delete '*'? [YES] [YES]". The people thought it rather strange, but went back to their work after moving the window beneath the browser.
So then I sent a dialog that wouldn't close that said: "Divide By Cucumber Error. Please Reinstall Universe And Reboot". The girl went and got a computer nerdish friend of her's and he looked at it, tried to make it go away, then finally shut down the computer and taped a piece of paper to the moniter saying 'I am sorry, but this machine is out of Order due to a "Cucumber Error".' [lol]
Are next prank is going to be in the most used elevator on campus. A motion-activated fart machine that waits until two or more people are in the elevator, the waits 10 seconds before playing the fart. We are using a BASIC stamp with IR LEDs for sensing how many people enter. Still trying to find the best place to actually place the main unit. The cieling has a lift up-panel, so we think that this will be the best place for it.