Howard: Look, I was going over the schematics on my zero-G toilet, and I made a teeny tiny mistake on the specifications for the diverter valve.
Leonard: How teeny tiny?
Howard: It's gonna fail after about ten flushes.
Sheldon: But the mission is for six months.
Howard: Yeah, see, that's the code red. It's kind of like a jack-in-the-box, no one knows exactly when, but at some point something way worse than a puppet is gonna pop out of that box.

Howard: You know, I'm really glad you decided to learn Mandarin.
Sheldon: Why?
Howard: Once you're fluent, you'll have a billion more people to annoy instead of me.

Howard: I invented a game. Want to play?
Leonard: Sure.
Howard: It's called Emily or Cinnamon. I give you actual quotes I've heard Raj say, and you guess if he was talking to his girlfriend or his dog.

Bernadette: Does your mother call you every day at work to see if you had a healthy lunch?
Howard: My mother calls me every day at work to see if I had a healthy bowel movement.

Howard: Hey, you want to make sure he gets nowhere with Penny without jeopardizing your friendship with either of them?
Leonard: I'm listening.
Howard: Just tell him to do everything you've done with her for the last two years.

Howard: Okay make your little jokes, but out of the four of us, I'm the only one who's making real world contribution to science and technology.
Rajesh: He's right, this is an important achievement for two reasons. Number one and of course number two!

Sheldon: Why does Leonard get to go?
Wolowitz: Because he's upset over his situation with Penny, and if I have to hear about it again, I'm gonna kick him in his ovaries!
Leonard: Thanks for understanding.
Howard: I've got your back, sister!