The One With Ross's Sandwich - S5-E9
Continuity mistake: During the literature class, when they're discussing Wuthering Heights all the writing on the blackboard changes, and the word "conflict" is first spelled correctly, but then it's spelled without the letter L.
The One With The Giant Poking Device - S3-E8
Other mistake: When Monica and Joey are holding containers of Ben and Jerry's, the brand name reads "En and Jer" and other parts of the containers have also been concealed, but we can still recognize the old Wavy Gravy in Monica's hand.
The One With The Flashback - S3-E6
Other mistake: When Phoebe's holding the box of Nabisco Nilla wafers, the Nabisco logo has stickers and paint hiding it and the Nilla is also partially covered so it reads "Villa" wafers.
The One With The Nap Partners - S7-E6
Continuity mistake: When Ross and Joey wake from their nap on the couch while everyone else is watching them, Marvin the Martian stuffed doll is lying on the floor between the couch and wall, but in the closeups Marvin the Martian is on the couch.
The One With The Metaphorical Tunnel - S3-E4
Continuity mistake: While everyone's watching Joey's commercial for the Milk Master 2000, the TV area changes in the closeups.
The One With the Sharks - S9-E4
Other mistake: While Monica, Rachel, and Joey are seated at the table talking about Joey's problem, there's a Dasani water bottle on the table with part of the brand name painted black so it reads "Asav" on the label.
The One Where Emma Cries - S9-E2
Continuity mistake: On the sign that reads 'It's a boy' Phoebe writes the word "not" with a black marker, then in following scenes such as when Monica and Chandler are talking about Tulsa, the word "not" is written differently on the sign.
The One With The Baby Shower - S8-E20
Continuity mistake: During the mock Bamboozled game with Chandler and Ross, when Joey asks about the word triskaidekaphobia a bottle of Evian suddenly appears on the countertop oven, which vanishes and then reappears.
Continuity mistake: After Ross decides to go after Rachel, in the overhead shot all four of the cab's doors are closed, but when it cuts to Ross and Phoebe getting in and shutting their front doors suddenly both back passenger doors are inexplicably wide open, then when Ross shouts about missing seatbelts both back doors are closed again. Then when the guy gets into the back seat he shuts his door, but when he asks for the medallion number both back doors are open, and then they're closed again.
The One Where Heckles Dies - S2-E3
Continuity mistake: After Monica breaks the seashell lamp, when Phoebe says that she wants to believe Monica did it accidentally her right is arm up and points to Monica, but in the next shot it's Phoebe's left arm that's up while still pointing at Monica.
The One with the Evil Orthodontist - S1-E20
Continuity mistake: When Rachel's in Barry's office her black handbag is hanging over the counter, but after Billy walks in on them and Barry pretends to look in Rachel's mouth, the bag's lying on the counter.
The One with the Evil Orthodontist - S1-E20
Continuity mistake: When Rachel walks into Central Perk she puts her black handbag down behind the couch and proceeds to talk about Barry, but after Ross smacks Chandler's arm to prompt him to speak up, the handbag's strap appears on Rachel's wrist.
The One with the Sonogram at the End - S1-E2
Continuity mistake: When Monica holds the glass pan of lasagna up over her head to try and find Rachel's ring, when it cuts to the next shot the lasagna is still in the air, but it's different - note burned corners, etc. (00:06:10)
The One With The Metaphorical Tunnel - S3-E4
Continuity mistake: When Ross is singing to Ben about GI Joe, there are two plates in the dish drainer behind him, but when Joey walks in and sits down the white plate has vanished.
The One With Ross's Tan - S10-E3
Other mistake: Chandler asks Monica "are you trying to do a British accent?" after she does an impression of Amanda. In the next shot, you see Chandler mouthing the line again.
The One Where Phoebe Runs - S6-E7
Visible crew/equipment: At the end when Ross is talking about his computer thing with Janine, a boom-mic can be seen above their heads. (00:21:55)
The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: When Rachel exits her bedroom and says she's going to London, you can see tape markings on the floor by her bedroom door and the end of the set. Furthermore, you can see a chair which is likely part of the Central Perk set. [Widescreen version]. (00:20:25)
The One Where Joey Moves Out - S2-E16
Continuity mistake: When Joey and Chandler are at Joey's colleague's brunch, you can see a big wall clock in some shots. You can see it when Chandler says: "Wow, there's my fantasy's come true" with the minute hand at five to the hour. Just a few seconds later, when Joey says: "Can you see me in a place like this?" it can be seen when Chandler is in shot, and the minute hand is now at 20 to the hour. (00:05:40)
The One With Joey's Interview - S8-E19
Continuity mistake: In the opening scene Rachel is holding a white felt pen in her hands and gesturing with it while she talks about the soap opera digest magazine. Between shots the pen sometimes has its cap on and then it's off again so you can see the blue tip. (00:00:20)
The One with George Stephanopoulos - S1-E4
Continuity mistake: When Ross wrestles his puck away from the little kid in the emergency room, it goes flying at the receptionist. The shot cuts, and it hits her from a completely different angle.
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.