Sheldon: Is your womb available for rental?

Sheldon: Well that's no threat, my mother's always wanted a grandchild.
Penny: Really? Your deeply religious born-again Christian mother wants a test-tube grandbaby born out of wedlock?
Sheldon: Curses.

Sheldon: Excuse me, but the problem is not solved. If your head had been accidentally amputated and we transplanted a dog's head in its place, would that be problem solved?
Leonard: If it were your head it would be.

Sheldon: If I would give you this gift basket, based on that action alone and no other data, infer and describe the hypothetical relationship that exist between us.
Store Clerk: Excuse me?
Sheldon: Here. Now, are we friends? Colleagues? Lovers? Are you my grandmother?
Store Clerk: I don't understand what you're talking about and you're making me a little uncomfortable.
Howard: See? Sounds just like you and Penny. We'll take it.

Store Clerk: Excuse me, Sir, you don't work here.
Sheldon: Yes, well apparently neither does anyone else.

Sheldon: *On computer screen* Greetings, hamburger toucher. You are probably wondering why you cannot IM with your little friends about how much you heart various things. Well, this recorded message is alerting you that I am putting an end to your parasitic piggybacking upon our WiFi. If you want to remedy the situation you can contact the phone company, set up your own WiFi and pay for it, or you may apologize to me.

Leonard: I just assumed. Who sells a full-sized time machine for $800?
Sheldon: In a Venn diagram that would be an individual located within the intersection of the sets 'no longer want my time machine' and 'need $800'.

Sheldon: That seems like an awful lot of trouble to go through for intercourse. Don't you have access to women who will do it for money?

Howard: Don't you think I should answer the engineering questions? I am an engineer.
Sheldon: By that logic I should answer all the anthropology questions because I'm a mammal.

Leonard: Howard brought a date?
Sheldon: A more plausible explanation is that his work in robotics has made an amazing leap forward.

Ramona: You are so witty.
Sheldon: Aren't I?

Sheldon: Given that Saint Valentine was a 3rd century Roman priest who was stoned and beheaded, wouldn't a more appropriate celebration of the evening be taking one's steady gal to witness a brutal murder?

Penny: Look, can we just forget about this extra stuff and can you just tell me what Leonard does?
Sheldon: Alright. Leonard is attempting to learn why subatomic particles move the way they do.
Penny: Really? That's it? Well, that doesn't sound so complicated.
Sheldon: It's not. That's why Leonard does it.

Penny: Sheldon, could I ask you a question?
Sheldon: I would prefer that you not, but I wouldn't go so far as to forbid it.

Sheldon: I wouldn't tell you the secret. Sssh!
Leonard: What secret? Tell me the secret.
Sheldon: Mom smokes in the car. Jesus is okay with it, but we can't tell dad.
Leonard: Not that secret, the other secret.
Sheldon: I'm Batman! Ssssh!