Sheldon: I'm quite aware of the way humans usually reproduce, which is messy, unsanitary, and based on living next to you for three years, involves loud and unnecessary appeals to a deity.
Penny: Oh, God!
Sheldon: Yes exactly.

Sheldon: (to Penny) Consequently, if Amy and I choose to bring new life into this world, it will be accomplished clinically, with fertility experts in a lab with Petri dishes. Which reminds me, you have broad hips, a certain corn fed vigor, is your womb available for rental?
Leonard: Still diggin' the Shami?

Penny: Can I ask you a question?
Sheldon: Given your community college education, I encourage you to ask me as many as possible.

Penny: There's a couple of things you should probably know.
Sheldon: I have a Masters degree and two Doctorates, the things I should know, I do know.
Penny: My point is, I know more about dating than you, and if you were as smart as you think you are, you would listen to me.
Sheldon: If you know so much, how come I have a date tonight and you have nothing better to do than drive me to it?
Penny: Fair point.

Rajesh: (to Howard) You slipped and fell into a robot hand?
Howard: Yes.
Rajesh: Penis first?
Howard: Yes. Now help me!
Leonard: I'd suggest a lubricant but I have a feeling you fell on some of that as well.