I had a dude come up to my register today and he bought some crap and paid with a $20. I was in a rush with other customers and hurriedly gave him his change. Before I can even close the till, he speaks up.
Dude: Hey! I gave you a $100! Where’s the rest of my change?
Terah: You gave me $20.
Dude: You little liar! I gave you a $100 dollar bill and you’re trying to cheat me! Where’s your manager?
Terah: Buddy, the $100 on the top of my stack is marked with a counterfeit pen, which I didn’t use during our transaction, and it’s stamped with a pink Piglet stamp. Unless you gave me a bill with a pretty, pink stamp on it, you’re a scam artist and I won’t hesitate to get security down here; they’re bored right now. Who’s next?
The dude sulked off after that.
Moral of the story is don't assume that because I'm in a rush I don't notice what you give me. I almost always notice.