Raj: Did you forget what Penny did to you? It took two years and defiling my sister to turn that frown upside down.
Leonard: I didn't defile your sister, we had a relationship.
Raj:I heard you called her Brown Sugar. In my book, that's defilement.

Sheldon: I want to build a road, but I need wood. Do either of you fellows have wood?
Raj and Howard: [Both chuckling]
Sheldon: I don't understand the laughter. The object of Settlers of Catan is to build roads and settlements. To do so requires wood. Now I have sheep; I need wood. Who has wood for my sheep?

Sometimes Howard and I pretend that his arrhythmia is acting up and I'm his sexy cardiologist. And the naughty part is I'm not in his HMO network.

Bernadette

Oh, no. They sent the wrong Spock. Live long and suck it, Zachary Quinto.

Sheldon

Penny: You mean, like a date?
Leonard: Not like a date, a date.

Amy: Jewelry? Seriously? Sheldon, you are the most shallow, self-centered person I have ever met. Do you really think that another transparently manipul... Oh! It's a tiara! A tiara. I have a tiara! Put it on me, put it on me, put it on me, put it on me, put it on me, put it on me, put it on me.
Penny: You look beautiful
Amy: Of course I do. I'm a princess and this is my tiara.
Sheldon: You were right, the tiara was too much.

Look, Howard, I'd say there's lots of fish in the sea, but I've seen you dangle your hook in that water for years, do not throw her back.

Leonard

I mean, even Donkey Kong had Donkey Kong, Jr., so he could teach someone how to kidnap princesses and throw barrels at Italian plumbers

Howard

Sheldon: I don't think there's anything in this jewelry store that Amy would appreciate more than the humidifier that we were just looking at at Sears.
Penny: Oh, my God, now I know what I sound like to you when I say stupid stuff.

Leonard: I don't know what to tell you, buy her something.
Sheldon: How does that work?
Leonard: Well, you skip over any attempt to repair your emotional connection and you win back her affection with an empty financial gesture.

You know digital alcohol is not the solution.

Leonard

Sheldon: Oh, I see why you're confused. No, her news sounded important, but what your forgetting is it was an achievement in the field of biology. That's all about yucky, squishy things.
Penny: Honey, she's upset. You're her boyfriend. You have to at least try to be excited by the things she's excited by.
Sheldon: What if they simply don't excite me?
Penny: Well, just smile and think about koalas.

The Big Bang Theory Season 5 Quotes

You can't blame yourself. When your prefrontal cortex fails to make you happy promiscuity rewards you with the needed flood of dopamine. We, neurobiologists, refer to this as the skank reflex.

Amy

I feel like two totally different people. Dr. Jekyyl and Mrs. Whore.

Penny