The One With All The Candy - S7-E9
Continuity mistake: When Ross is trying to convince Phoebe to try to learn to ride her bike again, the bike is completely covered by a large white sheet in the corner of Phoebe's room; however, in a later shot, the wheel of the bike is visible. (00:13:15)
The One With All The Candy - S7-E9
Continuity mistake: When Phoebe sits on the swing (when learning to ride her bike), her scarf has one end down her front and the other over her left shoulder. In the next shot, the end is over her right shoulder instead of her left. A couple of shots later, it is switched back again. (00:11:05)
The One With All The Candy - S7-E9
Revealing mistake: At the start of the episode, when Ross says, "No, one daddy, two mommies," Ben is mouthing the line along with him. (00:00:15)
The One With All The Candy - S7-E9
Continuity mistake: When Phoebe tries to show the gang she can ride her bike, the large metal bike rack at the curb changes position between shots. (00:09:50)
The One With All The Candy - S7-E9
Visible crew/equipment: After Ross gives Phoebe the bike and she is leaving to ride it for the first time, the stage lights are visible in the rear view mirror.
The One With All The Candy - S7-E9
Continuity mistake: In the scene where Monica's female neighbour comes begging for candy, after Monica gives it to her and shuts the door it's a man standing at the door not the neighbour.
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