I love this sequence from "The Chinese Restaurant" where poor George had to fart during sex and ended up ruining things:
Jerry: So what happened with Tatiana?
George: I shouldn't even tell you this.
Jerry: Come on...
George: Well, after dinner last week, she invites me back to her apartment.
Jerry: I'm with you.
George: Well, it's this little place with this little bathroom. It's like right there, you know, it's not even down a little hall or off in an alcove. You understand? There's no... buffer zone. So, we start to fool around, and
it's the first time, and it's early in the going. And I begin to perceive this impending... intestinal requirement, whose needs are going to surpass by great lengths anything in the sexual realm. So I know I'm gonna have to stop. And as this is happening I'm thinking, even if I can somehow manage to momentarily... extricate myself from the proceedings and relieve this unstoppable force, I know
that that bathroom is not gonna provide me with the privacy that I know I'm going to need...
Jerry: This could only happen to you.
George: So I finally stop and say, "Tatiana, I hope you don't take this the wrong way, but I think it would be best if I left".
Jerry: You said this to her after.
George: No. During.
Jerry: Oh, boy.
George: Yeah.
Jerry: Wow! So...?
George: So I'm dressing and she's staring up at me, struggling to compute this unprecedented turn of events. I don't know what to say to reassure this woman, and worst of all, I don't have the time to say it. The only excuse she might possibly have accepted is if I told her I am in reality Batman, and I'm very sorry, I just saw the Bat-Signal. It took me 3 days of phone calls to get her to agree to see me again. Now she's waiting for me to call her, and she's (gestures towards woman on phone) still on the phone!