A man is invited to Thanksgiving dinner at his girlfriend's parent’s house so that they can meet him. They've been together a while, but haven't had sex yet. His girlfriend tells him that after he meets her parents they can "get intimate".
In preparation, he decides to get some condoms at the local drugstore. As this will be his first time, he doesn't know anything about condoms and so he asks the pharmacist what he should buy. The pharmacist explains all about the differences between the brands and after a long chat the boy decides on a large box of "ribbed for her pleasure".
Evnetually, the time comes for the Thanksgiving dinner and the young couple are seated at the dinner table with the girl's parents. The girl is surprised to see the boy has his head bowed down apparently deep in prayer. She whispers to him, "I didn't know you were so religious!"
He whispers back, "I didn't know your father was a pharmacist."