Sheldon: (blows nose into tissue, shows family sitting at nearby table) Would you call that moss green or forest green?

Sheldon: Sadly Penny, this evening I am the dark knight roaming these mean streets alone. A windbreaker for my cape and a stern expression for my cowl.

Sheldon: When was the last time you had your menstrual cycle?
Penny: Oh, I'm not answering that Sheldon.
Sheldon: I'm going to say in progress.

Sheldon: I am very, very sorry for what I have done. Here's your laundry, I rescind your strikes and you are no longer banished.

Sheldon: Then I suggest you get them down with a long stick and play panty piata.

Sheldon: Howard?
Howard: Yeah?
Sheldon: Your shoes are delightful, where did you get them?
Howard: What?
Sheldon: Bazinga! I don't care.

Penny: How is that not talking to me like I'm an idiot? It's my friend, it's my couch, and it's my freakin' life!
Sheldon: It's also your roll.

Penny: I found the decaf.
Stuart: Oh, great.
Sheldon: Herbal tea for me, please.

Leonard: Sheldon, this date is probably my one chance with Penny. What happens if I blow it?
Sheldon: Well, if we accept your premise, and also accept the highly improbable assumption that Penny is the only woman in the world for you, then we can logically conclude that the result of blowing it would be that you end up a lonely, bitter old man with no progeny. The image of any number of evil lighthouse keepers from Scooby-Doo cartoons comes to mind.

Raj: They're going to digitally add a supernova they say its the perfect metaphor for my incandescent talent.
Sheldon: Yes, a giant ball of gas that collapses on itself.

Raj: (Talking about Leslie Winkle) I think she's smoking hot.
Howard: I'd hit that!
Sheldon: You'd hit particulate soil in a colloidal suspension. (Seeing Howard's confusion) Mud.

Sheldon: I couldn't sleep knowing that just outside my bedroom is our living room and just outside our living room is that hallway and immediately adjacent to that hallway is this!
Leonard: Do you realize if Penny wakes up there's no reasonable explanation to why we are here?
Sheldon: I just gave you a reasonable explanation.
Leonard: No, no. You gave me an explanation. Its reasonableness will be determined by a jury of your peers.
Sheldon: Don't be silly. I have no peers.

Sheldon: Would you like some aloe vera? 'cause you just got burned.

Sheldon: Hope you're not thinking about some sort of LSD thought control. Because there's only one mind-expanding drug this man enjoys, and that's called school.

Leonard: Are you drinking whiskey?
Sheldon: Indeed. If I'm to participate in the social convention that is the "stag night," then I must embrace all its components, including tobacco, swear words and, yes, alcohol. Jeepers, that's yucky!