The Coding4Fun site has a special page for April Fools' Day. You may or may not want to tell students about them. That all depends on your students. But you probably want to read what is there so you can recognize what kind of thing they might find on their own.
Of course buried in each "prank" is some serious learning and information about how some times work. There is a screensaver application, how to operate a CD trays and system sounds under program control, and a demo of how AutoCorrect in Word can "go bad." There are things there that you can use.
Geek humor may be different but that sure doesn't mean that it doesn't exist!