The jokes were some ui changes. The icon spinning backward and the progress bar saying April Fool’s in rainbow text every nth page load. A bouncing logo screen saver like behavior that would wipe a window that had been idle for X minutes (restored on mouse over).
I think there was one more, but the last I remember was the lead’s idea. After four (1?) hours idle, if you had audio enabled, you would hear the lead rapping his knuckles on his monitor and saying, “Hello? Is anybody there?” That could be funny or it could be terrifying.