Simon Helberg stars as Howard Wolowitz, the only one of the nerds that is not a doctor.  He is an engineer at Caltech and is friends with Leonard and Sheldon and frequently is over at their apartment.  Wolowitz mostly goes by his last name and still lives with his mother.

Most jokes with Wolowitz revolve around his failed attempts at womanizing, though he was given a girlfriend, Bernadette, in season three.

Howard Wolowitz Quotes

Sorry, Stallion. You're weird friend, Giraffe, is here.

Penny

Sheldon: I propose we add "pants must be worn at all times in the time machine"
Leonard: Seconded.
Wolowitz: I was gonna put down a towel

TBBT Quotes

James Earl Jones: Why don't you and your friends come to Comic-Con with me?
Sheldon: Really?
James Earl Jones: Of course. And San Diego is right across the border from my favorite city on Earth, Tijuana.... where I'm taking you every night!
Sheldon: Ay-yi-yi.
James Earl Jones: Ay-yi-yi. Bang. Bang.

Sheldon: Why do you have the Chinese character for "soup" tattooed on your right buttock?
Penny: It's not "soup," it's "courage."
Sheldon: No it isn't. But I suppose it does take courage to demonstrate that kind of commitment to soup.
Penny: How'd you see it? You said you wouldn't look.
Sheldon: Sorry. As I told you, the hero always peeks.