The Big Bang Theory2007

Sheldon:
[Knock, knock, knock] Penny. [Knock, knock, knock] Penny...

Penny:
What?

Sheldon:
[Knock, knock, knock] Penny. Zucchini bread.

Penny:
Ooh. Thank you!

Sheldon:
May I come in?

Penny:
No.

Sheldon:
Y - I see. Apparently, my earlier inquiry regarding you and Leonard crossed some sort of line. I apologize.

Penny:
Aw, thank you.

Sheldon:
So have you and I returned to a social equilibrium?

Penny:
Yes.

Sheldon:
Great. New Topic. Where are you in your menstrual cycle?

Penny:
What?

Sheldon:
I've been doing some research online and apparently, female primates - you know, apes, chimpanzees, YOU - they find their mate more desirable when he's being courted by another female. Now, this effect is intensified when the rival female, is secreting the pheromones associated with ovulation. Which brings me back to my question; where are you...

Sheldon:
[Penny slams door on his face] Clearly I'm 14 days too early.