The One With Phoebe's Birthday Dinner - S9-E5
Continuity mistake: Near the start, when Chandler asks if anyone else smokes, a woman with a brown jacket is seen getting a pack of cigarettes out her pocket. The camera cuts and now she has one in her mouth and is lighting it. (00:02:35)
The One In Massapequa - S8-E18
Continuity mistake: When Monica shows Chandler the photo of Chi-Chi, as she says, "It's good stuff, huh," in the closeup Monica takes hold of the photo with her raised empty right hand, but in the next wide shot Monica is holding a Sharpie in her right hand and the photo is in her raised left hand. (00:02:25)
The One With The Stain - S8-E7
Continuity mistake: After Gunther responds to Ross with the biting "ezels" retort, it cuts to Monica and Brenda in the living room, and when Monica falls off her chair, the rug and blue pad underneath are suddenly rolled up at the corner, then the rug is properly flat. (00:11:15)
The One Where Rachel Tells... - S8-E3
Continuity mistake: After the opening credits, when Joey and Phoebe enter Joey's apartment, note the poster hanging on the wall and some items on top of the fridge, as well as a few of the magnets on the fridge, change, move, vanish, or suddenly appear in the following shots. Examples: the wall poster moves closer to the door; the Chunky B. Wear magnet at the side of the fridge moves to the freezer door; a takeout menu suddenly appears on the fridge door; the red star magnet vanishes; etc. (00:03:00)
The One with the East German Laundry Detergent - S1-E5
Continuity mistake: The positions of the mugs shift between shots.
The One With The Halloween Party - S8-E6
Continuity mistake: When Joey is saying that he doesn't want to dress up, behind him is a guy with his shirt on top of his pants but in the next shot it is down. This happens throughout the whole scene. (00:00:35)
The One With The Stripper - S8-E8
Continuity mistake: When Mona is saying thanks to Ross for showing her his rock collection she puts her hair behind her ear, then when she's leaving she puts it behind again.
Continuity mistake: Rachel and Monica are talking about Phoebe getting pregnant at the table. Rachel's hands change every time where the camera is showing them in a different angle.
The One With Phoebe's Cookies - S7-E3
Continuity mistake: When Chandler and Jack are placing their robes on the hook, they change positions when Jack looks at Chandler naked. (00:19:39 - 00:20:08)
The One With The Hypnosis Tape - S3-E18
Continuity mistake: When Monica serves cheesecake to Pete, she goes to put the lid back, but in the next shot the lid is not there. (00:07:16)
The One with the Boobies - S1-E13
Continuity mistake: When Joey's mum explains that every day is like her anniversary, her hands are outstretched. Camera cuts and they are lowered. (00:18:20)
The One with the Boobies - S1-E13
Continuity mistake: The way Rachel is sitting when discussing seeing Chandler naked is constantly changing. (00:07:00)
The One with the Dozen Lasagnas - S1-E12
Continuity mistake: Second time we see Monica score on the foosball table, she spins the rod closest to the goal. The camera changes and the ball is hit from the rod furthest away from the goal. (00:17:35)
The One with Mrs. Bing - S1-E11
Continuity mistake: At the hospital, the positions of the balloons Monica brings change instantly. Note the blue one. Its height changes drastically from below to level with the yellow one. (00:11:30)
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 Where Underdog Gets Away - S1-E9
Continuity mistake: When Rachel turns up with her tickets, Chandler has his hand on his hip. As Rachel walks off however, his arm is behind her. (00:12:00)
The One Where Nana Dies Twice - S1-E8
Continuity mistake: In Central Perk, Joey says "So, Chandler looks gay huh?" When he does his arms are not crossed. Camera cuts and they are. (00:08:30)
Continuity mistake: When Ross is reading the book he shows it to Phoebe who passes it back. Then without turning the pages he passes it to Chandler but the pages are different now. (00:07:20)
Continuity mistake: When Joey asks how the play was, Monica's grip on her program changes between shots. Note the gap between her hands. (00:04:20)
The One with the East German Laundry Detergent - S1-E5
Continuity mistake: When the horrible woman says "no suds, no saves", Rachel's hands suddenly appear on her basket. (00:11:30)
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