The One With Monica's Boots - S8-E10
Continuity mistake: In The One With Monica's Boots, Monica is removing her trainers and replacing them with her boots so it looks as if she was wearing her boots all along. In one shot her left jean leg is tucked into her boots, but when she stands up it is sitting perfectly. (00:07:25)
The One With Monica's Boots - S8-E10
Continuity mistake: When Joey walks back into the apartment (with his eyes covered) to get the sandwich, he walks by the Fussball-table, and there's nothing on it. When he walks away you see a purse lying on the cooker. Then, when the shot changes to Dina and Rachel, you see the purse lying on the fussball table. (00:10:35)
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