The One With Rachel's Other Sister - S9-E8
Visible crew/equipment: When Monica heads to Joey's apartment to get the pies Joey tells her it's just one pie now, and after Monica's comment about losing the will to scold we can see the hole in the wall beside the front door.
The One With Rachel's Other Sister - S9-E8
Visible crew/equipment: When Monica tells Joey that he has a red plate instead of a fancy plate because it's a game, just as Joey says that he can't believe he won, we can see the camera at the right side of the screen.
The One With Rachel's Other Sister - S9-E8
Continuity mistake: When Ross, Rachel, and Amy arrive at Monica and Chandler's apartment the table is set, and there are folded napkins in napkin rings on the plates at each place setting, but after Amy insults Joey all the napkins have vanished.
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