An 18 year old male walks into a drug store. He says "I've been invited to Christmas dinner at my new girlfriend's house. Afterwards I hope there is a chance I get lucky, you know what I mean"
Clerk: "How about condoms then? They could come in handy. Here's a pack." The young man after paying walks to the door, stops, smiles, comes back: "you know what, the mom is also smoking hot, I think I'll take another pack, just in case I get extra lucky."
Christmas eve comes around, the boy sits at the dinner table and doesn't say a word. After a while his girlfriend says: "if I had known you were so quiet, I wouldn't have invited you." the young man replies "if you had told me your dad works at a drug store, I wouldn't have come."