The One Where Chandler Can't Remember Which Sister - S3-E11
Visible crew/equipment: When Phoebe and everyone else hear the guy upstairs with the "pogo stick" Joey gets up to give him the "butt kicking of a lifetime," and just as Joey walks around the couch we can see a crew member and camera, at the left side of the screen.
The One Where Chandler Can't Remember Which Sister - S3-E11
Continuity mistake: When Joey is saying about ticking his Grandma off, he has his hands up in front of him. When the shot changes, his hands are lowered. (00:13:20)
Answer: The statements that she's contradicting (that it is common, it happens to every guy, and it's not a big deal), are the things that a woman commonly says to a man who is suffering from erectile difficulty, typically to assuage his bruised ego. However, most men do not believe that these statements are true, as evidenced by Chandler's outburst. He's so caught up in the proof that women are lying about it that he gives himself away.
Rooster of Doom