A guy walks into a diner and orders a cup of coffee...

When the waitress sets the cup down in front of him, he notices that she's holding the cup in such a way that her thumb is literally in the liquid. Disgusted, but not wanting to cause a scene, he politely asks for a different cup and doesn't point out her faux pas. The waitress looks at him curiously, but complies, going back to the kitchen and returning with a fresh cup within a minute. Once again, her thumb is in the coffee. The man sighs and again orders a different cup with no explanation. Again, she looks puzzled but complies. When she returns with the third cup, yet again her thumb is in the coffee.

"Ugh!" He finally exclaims, unable to contain himself any longer. "Don't you realize that every time you bring me the coffee, you've got your thumb in my cup???"

"Oh, that!" She says in comprehension. "I'm sorry, but I have a very painful paper cut on that thumb and it soothes it to stick it in something warm."

"Then why don't you shove it up your arse?!" He says angrily.

"Oh, I do, every time I go back to the kitchen."