Adult Sheldon: I've always loved trains. In fact, if my career in theoretical physics hadn't worked out, my backup plan was to become a professional ticket taker. Or hobo.

Adult Sheldon: I didn't realize until years later that my father was only asking questions about lightning and thunder to cheer me up. In fact, he would often pretend to be dumb just to make me feel better.

Adult Sheldon: Ignoring things that irritate me isn't my strong suit. Obsessively fixating on them, now that's what gets me out of bed in the morning.

Adult Sheldon: My father didn't always get the credit he deserved. The advice he gave me actually worked out pretty well. Of course, I never told him.
George: Talked to Billy.
Missy: Why would you do that?
George: No, it was good.
Missy: Stay out of my life.
Adult Sheldon: He may not have been the world's greatest dad. But maybe we weren't the world's greatest kids.

Adult Sheldon: That was the first time I held my father's hand. I wouldn't touch my brother's hand until seventeen years later, thanks to the invention of Purell.

Mary: You understand that some people are going to be intimidated by you, because of how smart you are?
Sheldon: Or maybe they'll recognize my intellect and make me their leader.

Mary: How about we lose the bow-tie?
Sheldon: Why?
Mary: Look around, honey. No of the other kids are wearing one.
Sheldon: Well, perhaps I'll start a fad.