Rebecca states that the fact that Sam wears bikini briefs may reduce their chances of having a baby but there have been several episodes where Sam takes his pants off and not one time was he wearing briefs, he was always wears boxer shorts.
Norm: Cliff. Cliff. Cliff. His life is never gonna be the same after this.
Paul: Yeah, regular sex.
Norm: Wait a minute. I thought he said he was getting married.
Esther: We're going to have a great big chocolate wedding cake.
Cliff: Hold on there, ma. I'm allergic to chocolate, don't forget.
Esther: Then you may have graham crackers.
Cliff: Really? Wow.
Rebecca: I think I figured out why you haven't been able to give me a baby.
Sam: What makes you think it's my fault?
Rebecca: Well I've been doing some reading and I think I know what the problem is. You wear bikini briefs, don't you?
Sam: Sweetheart, I know the light's usually off but I do take them off.
Cliff: The only real hurdle left is ma. It's very traumatic when the woman you love more than anything else is the world meet your significant other.
Norm: Which would be which, Cliff?
Cliff: Now you see my problem.
Sam: Hey a new suit there, huh Cliff?
Cliff: Yeah. Like it?
Carla: Shiny as the penny you spent on it.