Quote from Elaine in The Fix-Up
Kramer: By the way, when you see George give him these, these'll work. Elaine: I knew those condoms were defective! Jerry: How did you know they were defective?! [George enters] Elaine: Because! Because she missed her period! George: She missed her period? Oh, my God. I can't believe it! I'm a father! I did it! My boys can swim! I can do it! I can do it! [runs out excitedly]