Howard: No ... about my job. I want you to tell me I'm good at what I do.
Sheldon: You're obviously good at what you do.
Howard: Well, then why are you always ripping on me?
Sheldon: Oh, I understand the confusion. I have never said that you are not good at what you do, it's just that what you do is not worth doing.

Howard's mother: It's this dress. When I put my front in, my back pops out. When I put my back in, my front pops out. It's like trying to keep two dogs in a bathtub.
Sheldon: What do you want me to do?
Howard's mother: We're going to have to work as a team. Get in here, grab a handful and start stuffing.

Sheldon doesn't know when he's being mean because the part of his brain that should know is getting a wedgie from the rest of his brain

Bernadette

Bernadette: You're being mean to him.
Howard: He's mean to me all the time. You've heard him tease me about not having a doctorate.
Bernadette: If you don't want to get teased about that, get a doctorate. I have one; they're great.

Sheldon: You don't think I'm condescending, do you?
Penny: Well....
Sheldon: Oh, I'm sorry. Condescending means....
Penny: I know what it means. And yes, you like to correcting people and putting them down.
Sheldon: Au Contraire. When I correct people I am raising them up. You should know, I do it for you more than anyone.

Penny: I know, he's the wheelchair dude who invented time.
Sheldon: That's close enough.

What are you all staring at? You ever seen a man try to get a meeting with Stephen Hawking before?"

Sheldon [in a French maid costume]

You make sissy on your belt buckles? Mee-Maw's forks never had that.

Sheldon

Sheldon: That's a lot of belt buckles.
Howard: Funny thing is, I only have one belt.

Howard: Let me try gangsta: Hells naw.

Leonard: Raj, you're our group historian. Has Sheldon ever begged before?
Raj: Three times. He begged the Fox network not to cancel 'Firefly.' He begged the TNT network to cancel 'Babylon 5.' And when he got food poisoning at the Rose Bowl Parade, he begged a deity he doesn't believe in to end his life quickly.

Howard: Sheldon, you are a condesending jerk. Why on earth would I want to do something nice for you?
Sheldon: Um ... to go to Jewish heaven?
Howard: Jews don't have heaven.
Sheldon: Then to avoid Jewish hell?
Howard: Have you met my mother? I live in Jewish hell.

The Big Bang Theory Season 5 Quotes

You can't blame yourself. When your prefrontal cortex fails to make you happy promiscuity rewards you with the needed flood of dopamine. We, neurobiologists, refer to this as the skank reflex.

Amy

I feel like two totally different people. Dr. Jekyyl and Mrs. Whore.

Penny