The One with the Monkey - S1-E10
Continuity mistake: When Rachel says about her 6th date with Paulo, she is holding a decoration for the tree. In the next shot the decoration changes to a much larger object. Then, in the next shot, as she hands it to Monica, it has turned back to the original shape. (00:05:40)
The One with the Monkey - S1-E10
Continuity mistake: Just after Chandler explains the situation to Janice, she goes off crying, and Ross takes a photo. The flash is much brighter than it should be - the screen's whited out to disguise a jump cut - after the flash Chandler's noticeably further back than he was before. (00:17:45)
The One with the Monkey - S1-E10
Continuity mistake: When Ross say 'just a smidge' after Rachel says Paulo named her breasts, Phoebe is holding tinsel and Rachel is looking at Ross. In the next shot, Rachel is looking in the opposite direction and the tinsel has vanished from Phoebe's hands. (00:06:00)
The One with the Monkey - S1-E10
Continuity mistake: When David kisses Phoebe in the lab the first time, he writes "yes" on the board. Later on when they are in the lab again the "yes" is different than the previous one.
The One with the Monkey - S1-E10
Continuity mistake: When Phoebe asks the guys if there is something they would like to share with the group, David goes from looking at his friend to looking at Phoebe between instant cuts. (00:05:05)
The One with the Monkey - S1-E10
Continuity mistake: Just before the opening credits, when Ross says, "That's 'pathet', which is Sanskrit for 'really cool way to live', " Marcel is sitting on Ross's left shoulder in the closeup, but in the next shot the monkey is suddenly sitting on his right shoulder, right before Ross walks off screen. (00:01:00)
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