Mine: banana guacomole. When I was first making guacomole, before I'd learned that you always open the avocadoes first, to be sure they're usable, I'd prepped up everything, got ready to add avos, and they were rock hard.
So I tried subsituting banana. On the basis that bananas are a bit like avocadoes. (They are high cal, and ripen off the vine.)
It was gross.