Sheldon: Geology isn't a real science!

Sheldon: If I could I would, but I can't so I shan't.

Sheldon: If it's good enough for Kirk, Crunch, and Kangaroo it's good enough for me.

Amy: A guest in my trundle bed and a boy at my door. I wish I could tell thirteen-year-old me it does get better.

Bernadette: (Yelling at Raj) I'M NICE TO EVERYONE!

Amy: You can't blame yourself. When your pre-frontal cortex fails to make you happy, promiscuity rewards you with the needed flood of Dopamine. We neurobiologists refer to it as the skank reflex.

Amy: Don't be so hard on yourself. Do you know the story of Catherine The Great?
Penny: No.
Amy: She ruled Russia in the late 1700s and one night when she was feeling particularly randy she used an intricate system of pullies to have intimate relations with a horse.

Penny: Coming. Yup, that's good. Wine glasses should have handles. (Answers the door to Amy)
Amy: Keeping accurate track of your alcohol intake. Smart idea considering how trampy you get when you've had a few.
Penny: You heard what I did?
Amy: I heard who you did.

Leonard: How could you not tell me your sister was moving back to India?
Howard: Maybe he was too busy writing clumsy penis metaphors about my fiancee.
Raj: Screw you, that was a beautifully-written penis metaphor.

Sheldon: What about Nebraska?
Penny: Oh hell with Nebraska. I'm gonna be a star!

Beverly Hofstadter: Hello, dear.
Leonard: You called my mother?
Sheldon: Oh, Leonard, is it really necessary to caption the obvious?
Beverly Hofstadter: He's been like that since he was a toddler. Look, Mommy, a butterfly. Maddening.

Beverly Hofstadter: Sheldon informed me that you're experiencing an emotional upheaval, and I'm here to help.
Leonard: That's so nice.
Beverly Hofstadter: And we're back to the obvious. Now, what's up?

Leonard: Well, uh, okay, um, I dont want to get back together with Penny. We tried it, it was crazy, it didn't work, but I can't deal with the fact that she slept with my friend Raj. And then I find out that Raj's sister Priya, who I've been going out with for eight months, is moving back to India. So I'm just completely confused and alone.
Beverly Hofstadter: I understand.
Leonard: Got any advice?
Beverly Hofstadter: Yes. Buck up.
Leonard: Excuse me. You're a world-renowned expert in parenting and child development, and all you've got is buck up?
Beverly Hofstadter: Sorry. Buck up, sissy pants.

Sheldon: Now, knowing Penny, the obvious answer is, they engaged in coitus. But, since that's what it looked like, we can rule that out. Let's put on our thinking cap, shall we? (Mimes doing so) Raj is from India, a tropical country. Third world hygiene. Parasitic infections are common, such as pinworms. The procedure for diagnosing pinworms is to wait until the subject is asleep, and the worms crawl out of the rectum for air. (Leonard spits out his food) Yes, just like that. Penny could have been inspecting Raj's anal region for parasites. Oh, boy. That's a true blue friend.
Leonard: They slept together, Sherlock.
Sheldon: No, you weren't listening. She said, it's not what it looks like.
Leonard: She lied.
Sheldon: Oh. Well don't I look silly sitting here wearing this?

Sheldon: That sounds like sarcasm, but I'm going to disregard it, because I have an agenda. Paintball. Specifically, the interdepartmental tournament this weekend. Now, in order to function better as a fighting unit, I thought we should establish a chain of command. Now, it goes without saying that I would outrank the three of you, but the question remains, by how much? Now, I don't see me as some four-star general, back at HQ riding a desk and playing golf with the Secretary of Defense. But I also can't be Sergeant Cooper, because that might lead you to think of me as just a regular Joe. This might take some thought. As you were.