The One With Rachel's Book - S7-E2
Continuity mistake: Chandler and Monica are having dinner with her parents. He asks Jack how he and Judy got engaged. He starts, "Well I'd gotten Judy pregnant..." Then they talk about how Jack told Monica's friends a "scary story" about how Judy got pregnant because her method of birth control, her diaphragm, had malfunctioned (damaged by a dog). In the rest of the show, however, we are continually hearing that the firstborn, Ross, was "a medical marvel" and that they thought Judy was barren. This apparently is the main reason why they love Ross more than Monica.
The One With Rachel's Book - S7-E2
Continuity mistake: When helmet-wearing Vicar Joey taunts Rachel one too many times she turns the tables on him, so when Joey backs away from Rachel he gets pushed up against the front door, and although he can't move, in the shot facing Joey he's at the left side of the door, but in the side shots he's at the right side of the door.
The One With Rachel's Book - S7-E2
Audio problem: Chandler, Monica and her parents are at dinner to discuss the upcoming wedding. When they describe how they remodeled the kitchen when she broke up with Richard, the camera pans to Monica and her mouth is moving but there's no sound. It then switches camera angles and Monica audibly asks, "Well what about when I started dating Chandler?" Which is what she said in the frame before with no sound. (00:11:00)
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