Have you ever forgotten to leave a tip?
Have you ever returned to pay a tip you couldn't leave (for forgot to leave) at another time?
Servers, have you had people apologize or return to give you a missed tip?
And/or: If you could design a restaurant, what kind of food would you serve, what would it look like, and what would you name it? What would set it apart from other restaurants? ETA: You don't have to run the restaurant at all, you're getting a (generous) flat fee for making the above decisions and then you're out.
Son of ETA: I forgot most of the people answering this question have always lived in a time of debit cards. :p The question was prompted by a conversation with my husband. We were talking about the craziest things we've done at restaurants. I was reminded of a time I thought I had more cash on me than I actually did and couldn't pay the tip (debit cards weren't a thing back then, yet). I felt so bad about it that the next day I went in and gave my server double the tip I should have and two movie passes to the theater nearby.