Stuart: Where are the kids?
Howard: I thought they were with you.
Stuart: What? No!
Howard: I'm kidding. They're at daycare.
Stuart: What about me makes you think my heart can handle that joke?

Stuart: Oh, Sheldon, I'm afraid you couldn't be more wrong.
Sheldon: More wrong? Wrong is an absolute state and not subject to gradation.
Stuart: Of course it is. It's a little wrong to say a tomato is a vegetable, it's very wrong to say it's a suspension bridge.

Howard: Hang on, I know a place where you could you stay and earn some money at the same time.
Stuart: Great!
Howard: I just have to warn you: it will involve humiliation, degradation and verbal abuse.
Stuart: So, what's the catch?

Bernadette: Hey, Stuart.
Stuart: *startled* Hey.
Bernadette: Sorry, did I startle you?
Stuart: Yes, but at this point pretty much any customer does.

Leonard: Just tell me the truth, Mother. Was my whole childhood just one big experiment?
Beverly Hofstadter: Of course not, dear. It was thousands of small experiments.
Leonard: So that's all I was to you, a-a test subject?
Beverly Hofstadter: No, you were my baby and I found you fascinating.
Leonard: Really?
Beverly Hofstadter: Yes, watching you develop, tracking your progress. I know I'm not the warmest of parents, but it was time we spent together, and, honestly, those are some of my fondest memories.
Leonard: When did you stop?
Beverly Hofstadter: Oh, I can't tell you. The experiment isn't over.

Raj: I never thought I would see Sheldon enjoying himself around babies so much.
Amy: Yeah, how about that?
Raj: So he just happened to stumble upon a book about experimenting with them the same day we were hanging out with Howard's kids?
Amy: Yep, don't overthink it.

Raj: Where are the kids?
Amy: Oh, Sheldon's helping Howard give them a bath.
Raj: Hmm. So you really think you can trick Sheldon into liking babies?
Amy: I slept with him. I married him. You want to bet against me?