Dr. Sheldon Cooper is Leonard's best friend, roommate, and co-worker at Calech. Sheldon is the smarter of the two with an IQ of 187, but is definitely the more socially awkward of two. He has a ridiculous ego, is extremely stubborn, but the group seems to put up with him.
Amy: Sheldon, there's something else I've been wanting to say, but before I do, I just... I want you to know that you don't have to say it back.I know you're not ready, and I don't want you to say it just because social convention dictates...
Sheldon: I love you, too.
Amy: You said it.
Sheldon: There's no denying I have feelings for you that can't be explained in any other way. I briefly considered that I had a brain parasite. But that seems even more far-fetched. The only conclusion was love.
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.