Newman was definitely one of the most popular recurring characters on Seinfeld, serving as Jerry's antagonist on the show.  Newman worked for the post office and often was a part of Kramer's schemes.

Newman Quotes

Is that Drake's Coffee Cake?

Newman

Newman: Kramer!
Kramer: Oh! That's Newman.
Newman: I'm on the roof!
Kramer: Well? What are you waiting for?
Kramer: You wanna shoot some pool tonight?
Newman: I can't, I'm goin' to the movies.

Seinfeld Quotes

George: Why don't they have salsa on the table?
Jerry: What do you need salsa for?
George: Salsa is now the number one condiment in America.
Jerry: You know why? Because people like to say "salsa." "Excuse me, do you have any salsa?" We need more salsa." "Where's the salsa? No salsa?"
George: You know, it must be impossible for a Spanish person to order seltzer and not get salsa. "I wanted seltzer, not salsa!"
Jerry: "Don't you know the difference between seltzer and salsa?! You have the seltzer after the salsa!"

Old Lady: What's bothering you? Is it my goiter?
Elaine: Goiter? What goiter?
Old Lady: This football shaped growth jutting out of my neck!
Elaine: Oh, noit's distinctive; as a matter of fact I wish I had one!