A teenage boys goes into the drugstore to buy some condoms for the
first time. The following conversation ensues:

Boy: I'd like to buy some condoms.

Pharmacist: Would you like the one-pack, the three-pack, or the
twelve-pack?

Boy: What's the difference?

Pharmacist: The one-pack is for young boys like yourself.

Boy: And what about the three-pack?

Pharmacist: The three-pack is for the big, strong college boys.

Boy: And what about the twelve-pack?

Pharmacist: The twelve-pack is for married guys like me.  (The boy
gets an astonished look on his face as the pharmacist continues.)
One for January, one for February, one for March.....