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!

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.

Leonard: How could you just sit there and let them spy on me?
Sheldon: They were very smart. They used my complete lack of interest in what you are doing.

Mrs. Wolowitz What's going on? Are you boys roughhousing?
Howard: We're just talking, ma.
Mrs. Wolowitz If you don't settle down right now, I'm not going to let you have any more sleepovers.

Sheldon: I'm baaaaaaaaaaaaaaaack.

Penny: So, do you think that if Leonard and I keep dating, Leonard would get bored with me?
Sheldon: That depends.
Penny: On what?
Sheldon: Do you have a working knowledge on Quantum Physics?
Penny: No.
Sheldon: Do you speak Klingon?
Penny: No.
Sheldon: Do you know any card tricks?

Sheldon: And you thought the opposite of stupid loser was a Community College Graduate?

Sheldon: When I try to deceive I have more nervous ticks than a lime disease research facility. It's a joke. It relies on a homonymic relationship between the tick the blood sucking arachnid, and tick the involuntary muscular contraction. I made it up myself.

Raj: Tag, you're it!
Howard: Shouldn't you put him in a brown paper bag and set him on fire?

Mrs. Wolowitz:What's going on? Are you boys rough housing?
Howard: We're just talking, Ma!
Mrs. Wolowitz: If you don't settle down right now, I'm not gonna let you have any more sleepovers.
Howard: For God's Sake, Ma, I'm 27 years old. And it's not even a school night.

Sheldon: I drank milk that tasted funny.

Raj: I hate trains.
Sheldon: Oh, don't be silly. You love trains.

Wolowitz: Leonard, how was your date?
Leonard: Bite me!

Leonard: Penny thinks I'm too smart for her. That's ridiculous!
Sheldon: I know! Most of your work is extremely derivative. And don't worry, that's not a secret.

Penny: Look, just forget I told you about me not graduating from community college, okay?
Sheldon: Forget? You want me to forget? This mind does not forget. I haven't forgotten a thing since the day my mother stopped breast-feeding me. It was a drizzly Tuesday.

Leonard: What happened to him?
Howard: He wouldn't sleep so I gave him a glass of warm milk with a handful of my mother's Valium in it. Tag you're it!

Wolowitz: Qu'est-ce que 'sup?

Sheldon: Why don't you just take your clothes down to the river and beat them with a rock.

Raj: They don't care for it if you stare at them and hyperventilate. Sadly, that's my homerun swing.

Raj: He was a lot more fun when he had no hope.
Howard: Give him time.

Penny: I meant has he ever been involved with someone who wasn't a brainiac?
Sheldon: Oh! Well, a few years ago, he did go out with a woman who had a Ph.D in French Literature.
Penny: How is that not a brainiac?
Sheldon: Well, for one thing she was French.

Howard: How's the air matress?
Sheldon: It's okay, if you don't mind sleeping on a bouncy castle.

Leonard: You could be Batman?
Sheldon: Yeah. I'm Batman. See?

Penny: It's just this is only our first date.
Leonard: Well, why don't we just figure out where we're going, and when we want to get there, and then rate of speed equals distance over time, solve for 'r'.
Penny: Or we could just wing it.