What's the dumbest mistake you've made that you'll never admit publicly?

I'll go first: I once prepped the wrong tooth for a crown. Patient was numb, I was distracted, and I prepped #13 instead of #14. Realized it halfway through. Had to explain to the patient why we needed to prep another tooth. I've never told anyone this. I'm so embarrassed. But I bet I'm not the only one who's done something stupid. What's yours? Let's normalize admitting mistakes so we can all learn.