The One With The Engagement Picture - S7-E5
Revealing mistake: In the shot of the paper with the picture of Monica and Joey, the anouncement written there starts out fine, but near the end the middle part is just repeated again. (00:20:35)
The One with the Dozen Lasagnas - S1-E12
Continuity mistake: When Rachel is talking with Phoebe about Paolo,. she unrolls some kitchen paper and uses it as a tissue. Initially she's holding two torn halves attached to the roll, then when saying "He's a pig" it goes to a whole sheet not attached to any others, then when she sits down it's a whole sheet attached to the roll again. Plus when Phoebe sits too, in some shots the paper is on the table, in others it's not. (00:15:20)
The One with George Stephanopoulos - S1-E4
Continuity mistake: When Rachel gets her first paycheck, the envelope is already open, but she then rips it open. (00:04:20)
The One with the Boobies - S1-E13
Continuity mistake: We've seen the arrangement of Joey and Chandler's bathroom in two previous episodes (1x3, The One with the Thumb, and 1x12, The One with the Dozen Lasagnas) with the sink opposite the bathroom door. In this episode the sink is relocated and the bath/shower is now opposite the bathroom door, for the rest of the series.
The One with the Ick Factor - S1-E22
Continuity mistake: When Monica takes off her belt and throws it onto the couch, it lands on Rachel's arm. Throughout the scene, between shots of Rachel and Monica talking, the belt constantly disappears, reappears and changes position without Rachel ever touching it. (00:05:25)
The One Where Emma Cries - S9-E2
Continuity mistake: When Rachel wakes up Emma during a nap, against Phoebe's advice, there is a shot of Emma in the cot. She is wearing a plain pink hat, but in the next shot, when Rachel lifts her out of the cot, she is wearing a white hat with what looks like little flowers on it. (00:05:55)
The One With a Chick. And a Duck. - S3-E21
Visible crew/equipment: Monica is talking to Pete in the diner when he gets back from Japan. If you look at the floor at Monica's end of the counter at the very beginning of the scene, you can see the mat that is there to protect her when she falls over later. (00:02:35)
The One with the Thumb - S1-E3
Continuity mistake: When we first see Chandler in his office, his sleeve is rolled below his elbow. In the next shot, it is above his elbow. (00:12:30)
The One With Princess Consuela - S10-E14
Continuity mistake: When Phoebe sits down in the coffee house and tells Chandler and Monica her new name, she takes her jacket off twice. (00:07:20)
The One with the Dozen Lasagnas - S1-E12
Continuity mistake: In the scene where Phoebe confesses to the gang that Paolo made a pass at her, it is pitch black outside. When Joey and Chandler turn around after heading for the door, it is sunny outside.
The One with the East German Laundry Detergent - S1-E5
Character mistake: In the laundromat, there is a sign where the word clothes is misspelt cloths. (00:16:00)
The One with the East German Laundry Detergent - S1-E5
Continuity mistake: While Rachel and Ross are at the laundromat there's laundry detergent, softener, bleach, etc., atop the soda machine, some of which change position or vanish in consecutive shots.
The One With The Proposal, part 1 - S6-E24
Visible crew/equipment: After Ross breaks up with Elizabeth, when she throws the water balloons at him and he starts walking away, a crew member's feet are seen standing on a windowsill behind Ross. Additionally, when Ross has exited the building, just as Elizabeth calls to him and he turns around we can see a crewmember, presumably standing beside the second camera, at the bottom left corner of the screen. We know it's not a passerby because he is as tall as the second story window behind him, which means he's elevated on a platform or ladder. (00:19:15)
The One with All the Poker - S1-E18
Continuity mistake: After the game at Ross' apartment Chandler takes Phoebe's cursed money, and when Ross wants to settle up with "the big Green poker machine who owes fifteen," Rachel's sitting down at the table in front of Ross, but then it cuts to Rachel who's suddenly standing up near the table. (00:12:30)
The One Where Chandler Can't Remember Which Sister - S3-E11
Visible crew/equipment: When Phoebe and everyone else hear the guy upstairs with the "pogo stick" Joey gets up to give him the "butt kicking of a lifetime," and just as Joey walks around the sofa we can see a crew member and camera, at the left side of the screen.
The One With All The Jealousy - S3-E12
Visible crew/equipment: After the barbershop quartet sing their "Ross song" to Rachel at her office, at the start of the next shot the camera can be seen at the right side of the screen, just as Ross walks out of Rachel's bedroom.
The One With The Rumor - S8-E9
Continuity mistake: When Ross hands Rachel the Yams in order to break the tension, the amount of food on both Ross' and Will's plates changes between shots. Also several wine glasses appear on the table. (00:12:30)
Visible crew/equipment: When Chandler points out to Joey that his oblivious comment was made in front of Ross it cuts to a closeup of Ross, and camera equipment can be seen at the right side of the screen, and it's still there in the next two closeups of Ross.
The One With The Fake Party - S4-E16
Continuity mistake: After Rachel explains her plan for the fake party, just as Emily opens the apartment door the message written on the Magna Doodle reads "Joey enjoys the," but when Emily and Ross are standing in front of the door the message reads "Joey eats little."
The One With The Fake Party - S4-E16
Visible crew/equipment: While Rachel's explaining how to play 'spin the bottle' the bottle she spins points to Gunther, and in the shot facing Gunther we can see the end of the set wall, at the right side of the screen.
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