The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: When Rachel opens the door to the apartment while she's holding flowers and sees Phoebe trying to get up from the couch (before the wedgie comment), the open edge of the set wall can be seen at the top left corner of the screen.
The One In Massapequa - S8-E18
Audio problem: When Monica is preparing her speech, she stands up to show Chandler her note card, but when you can hear her say "Hey, check this out," her lips don't move. (00:02:20)
The One Where Everybody Finds Out - S5-E14
Factual error: Phoebe holds up a bag of quarters that is almost the size of her head. This would be physically impossible for anyone except perhaps the world's strongest weight-lifters. Quarters are exceptionally heavy for their size. Two rolls weigh exactly a pound. It would take at least 300-400 rolls worth of quarters to fill up the bag Phoebe is holding, which means she is lifting 150-200+ pounds, primarily with one arm. (00:08:40)
The One With Joey's Big Break - S5-E22
Factual error: In the scene where Joey is supposedly in the Nevada desert, Saquaro cacti are seen in the background indicating that the scene was shot in Arizona or Mexico.
The One With The Giant Poking Device - S3-E8
Revealing mistake: In the scene where Chandler confronts Janice about Joey seeing her kissing her ex-husband, Janice begins to hyperventilate. However, right before Chandler gives her the paper bag, Janice spins around and places the receipt in her mouth. Conveniently, after she begins breathing into the bag, she "chokes" on a receipt. (00:10:07)
The One With The Triplets - S5-E3
Visible crew/equipment: In the scene with Joey filming Phoebe and Phoebe saying, "Please don't hurt me," Joey zooms out and you can see the camera that is just about to film them. (00:00:35)
The One With The Ball - S5-E21
Continuity mistake: When Rachel mentions the cat's name, Ross has the ball. The camera does an instant cut, and Joey now has the ball. Ross did not throw the ball, as you hear the ball being caught every other time. (00:04:50)
The One Where Ross Dates a Student - S6-E18
Continuity mistake: In the dinner scene between Chandler and the girl from college, the spoon in front of Chandler moves without him touching it. (00:13:45)
The One With Five Steaks and an Eggplant - S2-E5
Visible crew/equipment: In the part where Ross is on the phone with Julie he says "Say hi to Julie in New Mexico." When everyone is shouting "Hi Julie" look above their heads and you will see a boom mic dip into the shot. (00:03:10)
The One In Barbados, part 1 - S9-E23
Plot hole: This is actually for both parts of "The One in Barbados": it's shown that Monica's hair gets all frizzy from the humidity. And yet she's shown all throughout with her hair out and loose in all its frizzy glory, though it bugs her. I could maybe buy that not one of the women have hair gel with her (not bloody likely.) or that the fancy hotel doesn't sell hair gel (possible). But resourceful Monica would have thought of something to calm down her hair, or she would have just tied it up in a ponytail or bun - she does care a lot about her appearance. It makes no sense other than for comic value. (00:09:30)
The One Where the Monkey Gets Away - S1-E19
Continuity mistake: When Rachel asks Marcel 'did you poo in the shoe?' Marcel is leaning on Rachel's arm. In the next shot he has vanished. (00:06:10)
The One with the Blackout - S1-E7
Continuity mistake: At the start of the scene where the group disclose the weirdest place they've had sex is, Monica has her hands together on her lap. In the next shot, they are underneath her legs. (00:05:30)
The One Where Chandler Gets Caught - S10-E10
Continuity mistake: After Chandler says he loves the house, Monica says "this is huge" with her arms by her sides. We then cut to a front shot, and Monica's holding her hands in front of her. (00:04:30)
The One with the Sonogram at the End - S1-E2
Continuity mistake: At the very start of the episode, Monica holds up both of her hands. In the next shot her right hand is wrapped around her legs. (00:00:05)
The One With Ross's Tan - S10-E3
Continuity mistake: When Ross gets a spray on tan, there is one shot where he is being sprayed in the face. Instant camera cut then it's on his chest, not near his face. (00:19:35)
The One With The Cake - S10-E4
Continuity mistake: When Ross and Rachel are driving back, Ross starts to put the seatbelt on. Instant cut, and he has his seatbelt on. (00:17:35)
Continuity mistake: In addition to Ross remaining 29 for several years, he also gets younger as the years go by. When he marries Emily he is thirty (Monica describes herself as "a single mother with a 30 year old son"), but when he divorces her he is twenty-nine.
The One with the Candy Hearts - S1-E14
Continuity mistake: Just after Rachel throws a bread roll at Joey, he turns to Chandler to speak to him. Chandler is holding his hands out in front of him. In the next shot, his right hand is touching his face, then in the next shot, it is lowered again. (00:02:55)
The One With The Blind Dates - S9-E14
Visible crew/equipment: When Phoebe meets Joey to tell him about the date for Rach, the stage lights are seen outside the coffee-shop. (00:05:35)
The One Where Nana Dies Twice - S1-E8
Continuity mistake: In this episode, Rachel tells Chandler that she thought he was gay until he spent Phoebe's entire birthday party talking to her breasts. But at this point since Rachel joined the group, Phoebe hasn't had a birthday yet; that occurs some episodes later, in "The One With Two Parts." (00:02:00)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.