Mrs. Wolowitz: Who's there? Are you a sex criminal?
Howard: Sex criminals don't have key, ma!
Mrs. Wolowitz: Where were you so late?
Howard: I was out with Bernadette
Mrs. Wolowitz: I know what that means, I watch Dr. Phil. I hope to God you used a condom.
Howard: I am not having this conversation with you, ma.
Mrs. Wolowitz: God forbid you get one of them fancy sex diseases.
Howard: Nobody has a disease!
Mrs. Wolowitz:I hope not. I share a toilet with you. Is that what you want, to give your mother herpes?

Amy: So, you feeling better?
Penny: Not really.
Amy: Sheldon, you have a guest who's upset.
Sheldon: I'll make tea.
Penny: Sweetie, it's OK. I don't want tea.
Sheldon: It's not optional.

Sheldon: Priya, if you're experiencing any tension or awkwardness, it may stem from the fact that Leonard and Penny used to, if I might quote Howard, "Do the dance with no pants".

Amy: Thanks to you, I just made a rhesus monkey cry like a disgraced televangelist.

Raj: You heard me, I forbidded it.
Priya: Forbidded it?
Raj: Forbayded it?

Sheldon: Just keep in mind, should you ever need a slightly apathetic, tertiary friend, I stand at the ready.

Amy: Well, granted Penny your secondary sexual characteristics are reasonably bodacious but Priya is highly educated, she's an accomplished professional and she comes from the culture that literally wrote the book on neat ways to have sex. Whereas you, on the other hand, are a community college drop-out who comes from the culture that wrote the book on tipping cows.

Amy: I came as quickly as I could.
Penny: Ok, why?
Amy: To comfort you, of course. Sheldon told me about Leonard dating Rajesh's sister, so I high-tailed over here to pick up the pieces of your broken heart.
Penny: Amy, I'm fine.
Amy: You don't have to be strong for me. Now, let's talk about Priya, that man-stealing bitch.

Sheldon: The Hindu Code of Manu is very clear in these matters. If a woman's father is not around, the duty of controlling her base desires falls to the closest male member of her family. In this case, Raj. The code also states that if she disobeys, she will be reborn in the womb of a jackal and tormented by diseases. If true, that seems like an awfully large gamble given that the prize is Leonard.

Sheldon: Leonard, social protocol states when a friend is upset, you offer them a hot beverage, such as tea.
Howard: Tea does sound nice.
Sheldon: You heard the man, Leonard. While you're at it I am upset we have an unannounced house guest, so make me cocoa.

Penny: Ooh, I thought I smelled pizza.
Sheldon: That's remarkable. If pepperoni were an explosive substance, you could replace German shepherds at our nation's airports.

Amy: It seems like the appropriate thing to do when one's best friend finds herself replaced by a smart, beautiful woman with the smouldering sexuality of a crouched Bengal tiger.

Sheldon: Point of inquiry. Given that Leonard is your secondary friend and Koothrappali is your primary friend, why didn't you seek refuge under his roof?
Howard: There's no room. His sister is staying with him.
Leonard: Wait, wait. What?
Sheldon: Cocoa, Leonard. Focus. I'm down in the dumps here.

Sheldon: Don't worry. As you tertiary friend I'm prepared to step in and comfort you.
Howard: It's not really necessary.
Sheldon: Ah no. I'll finish making the tea while you narcissistically ramble on about whatever's troubling you.
Howard: Thanks.
Sheldon: That's what tertiary friends are for.

Penny: I'm sorry. I didn't know you had company. I don't want to impose.
Sheldon: No, no. It's not an imposition. At this point, in our ecosystem, you are akin to the plover, a small scavenging bird that eats extra food from between the teeth of crocodiles. Please, fly into our open maw and have at it.