The One With The Home Study - S10-E7
Continuity mistake: When Phoebe and Mike first donate the money to the children, the way the man is holding the cheque changes depending on the shot. (00:03:15)
The One With The Home Study - S10-E7
Continuity mistake: When Mike says "I am going to make this decision for us. What do you think we should do?" he is holding the check. The very next shot shows the charity worker taking the check off the desk and giving it back even though Mike never put it down. (00:20:35)
The One With The Home Study - S10-E7
Continuity mistake: When Ross and Rachel are pushing Emma on the swing, the legs of Emma's pants change position several times between shots. At first they are pulled up with her legs exposed, then they are down further, and in the last shot when Ross gets kicked, they are pulled up again.
The One With The Home Study - S10-E7
Continuity mistake: When Chandler kisses Monica before letting the social worker in, she puts her hand on his arm. The camera cuts to her and she says "Tongue, really?" but her hand is by her side now. The camera cuts back to Chandler and both her hands are now out in front of her.
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