@farmerman,
It's funnier in context with the show leading up to the gaffe but,
Larry says to Bill, so we're both members of the zipper club.
Earlier, one of the silly questions the others asked Larry was, button fly or zipper so the context was set. Later on it was pointed out to Larry that maybe he should clarify the remark. Bill says it's a good thing you clarified.
He meant heart surgery
The look on Larry's face when he realized...... classic.