Every year, when April Fool's falls on a school day, I get to play a joke on my students.
I add a Title to the top of the document, and at the bottom create a list of words from whatever unit we are currently studying for them to find in the "word search."
However, the only real words are "april fools."
I'll give this to them the last 5 minutes of class and keep quiet while they try to find the words. They usually get a kick out of it and ask for copies to bring home to their parents and siblings. :)