secret banana writing
No, this entry isn't about the letter-tile game Bananagrams. (Some of my friends love it; if you're unfamiliar with it, take a look. But it doesn't really fit my head for some reason.)
Instead, this entry is a link to the Bloggess's entry about how to write magically appearing notes on a banana.
Just write on a banana skin with a toothpick, and a few hours later, the words you wrote will become visible. Cute!