Penny: You know, I do understand what you're going through.
Sheldon: Really? Did you just have the Nobel Prize in Waitressing stolen from you?

Leonard: Why would you buy peppermint schnapps?
Penny: Because I like peppermint, and it's fun to say schnapps!

Oh man, did the KISS Army repeal "Don't Ask, Don't Tell?"

Penny [after seeing Wolowitz in his goth outfit]

Penny: I'll tell you what, next french toast day, I'll make you oatmeal
Sheldon: Good lord, are you still gonna be here next french toast day?

Penny: I give up, he's impossible
Sheldon: I can't be impossible, I exist. I believe what you meant to say is, "I give up, he's improbable."

Sheldon: Yes, since their relationship became carnal, Penny has updated his designated term of endearment, distinguishing him from those she calls "sweetie," usually as an attempt to soften a thinly-veiled insult.
Penny: You're boring people, sweetie.
Sheldon: Although sometimes, she omits the veil entirely.

Wolowitz: So, what are we watching? Sex in the City, yikes!
Penny: Hey, I happen to love this movie.
Wolowitz: Fine, let's watch it. Maybe all our periods will synchronize

Leonard: You know deep down on the inside, Howard's a good guy
Penny: The problem isn't what's on the inside, it's the creepy candy coating

Sheldon [filling out medical form]: When was your last menstrual period?
Penny: Oh! Next question!
Sheldon: I'll put in progress

Sheldon: Why do you have the Chinese character for "soup" tattooed on your right buttock?
Penny: It's not "soup," it's "courage."
Sheldon: No it isn't. But I suppose it does take courage to demonstrate that kind of commitment to soup.
Penny: How'd you see it? You said you wouldn't look.
Sheldon: Sorry. As I told you, the hero always peeks.

Wolowitz [about Bernadette]: She wants a commitment, but I'm not sure if she's my type.
Penny: She agreed to go out with you for free. What more do you need?

Penny: I'm a Sagittarius, which probably tells you way more than you need to know.
Sheldon: Yes, it tells us that you participate in the mass cultural delusion that the sun's apparent position relative to arbitrarily defined constellations at the time of your birth somehow affects your personality.
Penny: Participate in the what?

TBBT Quotes

Oh, Bernadette, please play my clarinet.

Raj's poem

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?