Principal Petersen: If you don't want another one, do what I did.
George: I'm not getting a divorce.
Principal Petersen: No, I mean, get a little snip. Never worry about it again.
George: Well, you mean like a... like a down-there snip?
Principal Petersen: I can't believe I let you teach Health.
George: Well, Mary'd never go for that.
Coach Wilkins: I didn't know you got snipped.
Principal Petersen: That's 'cause my balls are none of your business.
Coach Wilkins: Fair point.

Sheldon: You wanted to see me?
Principal Petersen: When don't I want to see you, Sheldon? Come in. I have something I'd like to give you. This is a key to the faculty restroom. No students allowed. One person at a time. And unlike the other restrooms, this one gets cleaned every night.
Sheldon: Thank you.
Principal Petersen: No, Sheldon. Thank you.
Sheldon: You're welcome.

[on the "Why Sheldon Cooper Should Go to College" tape:]
Principal Petersen: A student like Sheldon comes along... once in a lifetime. This school is not gonna be the same without him. But I know he's gonna do great things. And I'm honored to have been a small part of it.

George: Hey, Tom, you got a minute?
Principal Petersen: Pretty busy. Make it quick.
George: It turns out I don't need that raise.
Principal Petersen: What happened, you win the lottery?
George: No, no.
Principal Petersen: Aw, George, I am so sorry.
George: Well, what can you do?
Principal Petersen: Listen, I cleared your raise already, why don't you just keep the money.
George: Oh, no, I couldn't do that.
Principal Petersen: No. No, I mean it. It's yours.

Adult Sheldon: I always believed my extraordinary life would be chronicled in numerous biographies. I even used to make up my own titles. My favorites were: "From Texas to Success: the Sheldon Cooper Journey", and "Cooper for Kids", a pre-school introduction to quantum gravity in superstrings. The point is, I knew my formative years would be well-documented, which meant I needed to polish up some of my early academic credentials, especially East Texas Tech.

Sheldon: If W is the Kähler metric on the algebraic variety X, and the canonical bundle KX is trivial, then X is what?
Dr. John Sturgis: A Zariski space.
Sheldon: Wrong. [slaps Dr. Sturgis's hand with his pencil]
Dr. John Sturgis: Hey!
Dr. Linkletter: Obviously, it's an elliptic curve.
Sheldon: Wrong. [slaps Dr. Linkletter's hand with the pencil]
Dr. Linkletter: Hey!

Dr. John Sturgis: Why are you hitting us?
[flashback:]
Mei-Tung: Wrong.
Sheldon: Ow! Why'd you hit me?
Mei-Tung: Pain is the best teacher.
[present:]
Sheldon: I'm teaching you.
Dr. Linkletter: Well, it feels like you're hitting us.
Sheldon: Like you, I struggled with these concepts, but eventually, I mastered them, through hard work, resilience and a healthy dose of knuckle whacking.