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 Where Chandler Doesn't Like Dogs - S7-E8
Continuity mistake: In this episode, it is stated that Ross does not like ice cream because it's too cold. However, back in The One Where Ross Dates a Student, you can see Ross on a date with Elizabeth eating an ice cream.
Factual error: Phoebe's greatest love David leaves her to go to Minsk and comes and goes throughout the whole show, telling stories of Minsk on the way i.e. of the long months when the sun does not rise and the constant freezing cold. Minsk, being the capital of Belarus (although claimed to be in Russia for reasons explained in Corrections), is approximately as high up north as i.e. Wales and northern coast of Germany, and even during the winter months there is always daylight for several hours. Although winters in Eastern Europe are cold, the kind of coldness described by David would more believably happen in Siberia than Minsk, and the summers are just as nice and hot as everywhere in Europe.
The One With The Cheap Wedding Dress - S7-E17
Continuity mistake: Monica chooses a wedding dress at an expensive boutique, then later goes to a discount store to buy the same style dress at a half-off sale. The dress she buys is different from the one in the boutique, having wider and frillier straps. When she tries it on later at the apartment, it is now the same style as the one at the boutique. (00:04:00 - 00:07:15)
The One Where Monica Gets a Roommate - S1-E1
Continuity mistake: When Ross, Chandler and Joey are setting up Ross' furniture and Ross is bent down saying, "And I cannot feel my legs," Ross is holding up a manual. When it cuts, the manual is suddenly lying on the floor. [In other versions, such as Netflix, the first shot shows the manual falling to the floor and the second shot does not exist. However, the mistake is valid for the TV broadcast version of the episode]. (00:11:45)
The One With The Baby Shower - S8-E20
Visible crew/equipment: Monica chases after Rachel's Mom to apologise and she falls over and you can clearly see the safety mat move when Monica falls on to it - it's blue and just down the first step. (00:22:00)
The One With All The Thanksgivings - S5-E8
Continuity mistake: In the flashback where Joey sticks the turkey on his head, the subtitle says Thanksgiving 1992. However, the show started in 1994 and Joey didn't move in until the previous fall, so the earliest Thanksgiving that he was there would have been 1993. (00:04:30)
The One With The Mugging - S9-E15
Revealing mistake: When Rachel tells Joey that his agent called and he got the audition for the Broadway play, Rachel's wearing a colorful paisley top, and after Monica says, "Maybe the monkey will be at the audition," in the next shot it's Jennifer Aniston's stand-in, wearing a red plaid blouse, who is standing beside Joey. (Widescreen). (00:03:08)
The One With The Proposal, part 1 - S6-E24
Continuity mistake: In the scene where Richard is being seated next to Chandler and Monica, the amount of champagne in Chandler's glass changes. (00:09:20)
The One With Rachel's Other Sister - S9-E8
Other mistake: When Joey and Phoebe are talking while Rachel and Amy are fighting, Phoebe says the line 'Oh my God. Shouldn't we stop this?', Joey is mouthing her lines. (00:20:25)
The One with the Blackout - S1-E7
Revealing mistake: When Rachel first meets Paolo she's looking for the cat in candlelight, holding the candle in front of her. You can see her shadow on the wall, as well as the shadow of the candle, revealing that the light is not coming from the candle. (00:07:25 - 00:14:30)
The One After Ross Says Rachel - S5-E1
Audio problem: Monica tells Ross that he should keep looking for Emily, and Chandler says "Yeah, for about 30 minutes." But the audio doesn't match up with his lip movements, indicating this line was dubbed. (00:10:26)
The One With All The Wedding Dresses - S4-E20
Visible crew/equipment: When it's Monica's turn to catch the bouquet she and Phoebe switch places, and just as Phoebe asks her if she's ready, in the wideshot studio lighting rigs can be seen at the top of the screen.
The One Where Ross Got High - S6-E9
Visible crew/equipment: After Ross and Monica blurt out each other's secrets to their parents, when Jack says, "And we kind of figured about the porch swing," in his closeup we can see the end of the set wall, with the soundstage behind it and many tape marks on the floor.
The One In Massapequa - S8-E18
Visible crew/equipment: After the anniversary party, when Rachel and Ross are back at the apartment and Ross tells her that it was the easiest four hundred bucks he ever made, Rachel gets up and just as she walks around the couch we can see the reflection of the cameraman/crew member in the mirror on the wall, at the right side of the screen.
The One Where Rachel's Sister Babysits - S10-E5
Continuity mistake: Rachel and her sister are in Rachel's room. When Rachel picks up Emma, Emma has nothing in her arms, but in the next shot when Rachel is holding her, she has a toy in her arms though she had no time to get one.
Continuity mistake: The view from Monica's apartment changes after the first few episodes.
The One With a Chick. And a Duck. - S3-E21
Continuity mistake: When Ross is asking Joey and Chandler which suit he should wear for the TV thing the brown suit is in his right hand and the blue one is in his left hand. After Ross says "really?" the shot changes to a wide view, the two suits have changed places, and the cover on the brown suit has switched to the blue one. (00:09:50)
Continuity mistake: The Chick changes breeds and gender a couple of times. It starts out as a full size White Leghorn. During the adolescent phase it is a female White Silkie. This is a bantam or small size chicken. In maturity it is a male White Leghorn.
The One With The Fertility Test - S9-E21
Continuity mistake: When Rachel takes her gift certificate to the massage parlour to claim her free massage, she hands it to the receptionist and we can see that it has been torn up into eight pieces and taped back together. Yet when Phoebe tears up the gift certificate in a previous scene, we see her tear it into only four pieces before handing it back to Rachel. (00:05:00 - 00:08:20)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.