SEINFELD Episode no. 119 "The Sponge"
ELAINE: New jeans?
JERRY: Yeah.
ELAINE: Still a 31 waist?
JERRY: Yep. Since college.
New scene - George and Susan in George's car.
SUSAN: You know, I really like those new jeans Jerry was wearing. He's really thin.
GEORGE: Not as thin as you think.
SUSAN: Why? He's a 31. I saw the tag on the back.
GEORGE: The tag, huh?
SUSAN: Mmm-hmm.
GEORGE: Let me tell you something about that tag. It's no 31, and uh...let's just leave it at that.
SUSAN: What are you talking about?
GEORGE: He scratches off a 32 and he puts in 31.
SUSAN: Oh, how could he be so vain?
GEORGE: Well, this is the Jerry Seinfeld that only I know.