[Kurt looking at Sheldon who is dressed as the Doppler Effect]
Kurt: So what are you, a zebra?
Sheldon: [to Leonard] Yet another child left behind.

[Missy is leaving and Sheldon is saying goodbye to her.]
Sheldon: OK, well, it was pleasant seeing you, other than that business with my testicles. [Puts his hand out for her to shake]
Missy: Come on Shelly. [Gives him a hug, which Sheldon does as well.]
Missy: I want you to know I'm very proud of you.
Sheldon: Really?
Missy: Yep. I'm always bragging to my friends about my brother, the Rocket Scientist.
[Sheldon looks in disbelief.]
Sheldon: You tell people I'm a Rocket Scientist?!
Missy: Well yeah.
Sheldon: I'm a theoretical physicist.
Missy: What's the difference?
Sheldon: What's the difference?!
Missy: Goodbye, Shelly.
Sheldon: My God! Why don't you just tell them I'm a toll taker at the Golden Gate Bridge! Rocket Scientist, how humiliating!

[Sheldon is singing "L'Chaim" at Penny's bar]
Leonard: I don't believe it. What's gotten into him?
Penny: [holding up a bottle of Bacardi] Oh, a couple of virgin Cuba Libres who turned out to be kinda slutty.
Leonard: [excited] You didn't!?
Penny: Hey, you do your little experiments, I do mine.

[While Sheldon is listening to a tape, Penny comes from behind and touches his shoulder, which scares him.]
Penny: Sorry, Sheldon. Do you have a second?
Sheldon: A second what? Pair of underwear?
Season 2