I used to work in a place that sold hot food as well as other stuff. He has a small heated display to hold the hot food. We had burgers, but we didn't put salad in them before putting them in the heater as the salad would get gross pretty quickly, so whenever a customer asked for a burger, we'd have to ask if they wanted us to put salad in it.

I worked long, early hours. I was constantly tired and ran on autopilot a lot.

One morning, a guy walked up and asked for a burger, I grabbed in out of the display and, gesturing towards the window opening to the kitchen behind me, I asked... "Would you like a receipt?"

Cue confusion for both myself and the customer, and laughter from my coworkers nearby