The numbers keep getting bigger. I don't think this still fits on a giant novelty check signed by Serena Williams.
(Link.)
Edit: also, 17 and 2 must be like your lucky numbers.
I did actually pull of a prank this year. I told my chemistry students from here on they'd be learning secret alchemical knowledge. In the class I had on the early morning one or two people were scrambling to take notes. In the later class I noticed some more people glancing around with an "I know what's going on" look, but they did find it funny.
I hope it doesn't catch on, I could recycle this one for years.
Also, if you're one of my students and happen to have stronger google-fu than I gave you credit for: uhh, hi?