I had a fantastic math professor in my bachelor of engineering program. Besides promising to do handstand in the last lecture if everybody submitted the teacher evaluation, he would tell math related anecdotes. One about a high school friend, whom just loved the concept of greek letters so much that he invented his own greek letters, upper and lower case. During his hand ins he would regularly define variables as his own invented letters, paw, py or ypricon, and alledgedly did so at his oral exam, causing the censor to be highly confused and embarrased to not be familiar with those characters.

For sure a think-out-of-the-box move, and a good prank for a math teacher