What Dirty Tricks Did You Use for April Fool's?

zxnos asks: "What evil, underhanded, dirty mean trick did you pull on April Fool's Day? Since I arrive in the office first, I wrote a little routine to go off when my coworkers tried to open the application that we all work in. It said: "Sorry, you arrived late for work today. The application you have requested is unavailable." The only response was 'OK' and would then close the application. What did you do?"