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 Where Chandler Can't Cry - S6-E14
Visible crew/equipment: While Rachel's looking out Monica and Chandler's window she tells Joey that Ross is on a date with her sister, and just as Joey comments, "I didn't know we could date your sister," a crewmember can be seen moving around near the front door at the left side of the screen, and we know it's not Chandler or Monica since they're still in the bedroom wearing robes in the next shot.
The One Where Chandler Can't Cry - S6-E14
Continuity mistake: When they're watching the vampire video, Monica, Chandler, and Rachel are sitting on the couch, but in the closeups of the TV we can see the couch in the reflection and it's empty.
The One In Vegas, Part 1 - S5-E23
Continuity mistake: After Joey tells Chandler about his identical hand twin and plans for getting rich, when he sees Chandler's reaction Joey asks, "Are you unsupporting me again?" while he lifts his left arm and points accusingly at Chandler, but next shot it's Joey's right arm that's up and pointing.
The One Where Ross Can't Flirt - S5-E19
Other mistake: While everyone's watching Law and Order for Joey's big scene, Rachel, Phoebe, Monica, and Chandler are sitting on the couch and Ross is standing behind them, but in the TV's closeup the screen reflection reveals an empty couch.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: While Joey's looking for the "hot girl" the second time, after he knocks on the little girl's door and asks if her mother, sister, or babysitter are a hot girl, he runs off when she shouts for her father, and when Joey stops in another hallway full of doors the shadow of the moving boom mic can be seen on the door beside him.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: When Rachel gets back from her first interview, just as Chandler says, "Oh hey," we can see the boom mic at the top of the screen.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: When Joey is standing at Monica's window waving to Ross, the end of the set wall with movement on the soundstage can be seen at the left side of the screen.
The One Where Everybody Finds Out - S5-E14
Visible crew/equipment: When Ross is using the binoculars to watch Ugly Naked Guy's apartment, the end of the set wall can be seen behind him.
The One Where Everybody Finds Out - S5-E14
Visible crew/equipment: When everyone's looking out Monica's window into Ugly Naked Guy's apartment, and see all the gift baskets he's been sent, the end of the set wall in Monica's apartment can be seen.
The One Where Everybody Finds Out - S5-E14
Visible crew/equipment: While Phoebe and Rachel are at Ugly Naked Guy's apartment, when Phoebe looks out the window and sees Monica and Chandler the end of the set wall in Monica's apartment can be seen.
The One With The Inappropriate Sister - S5-E10
Visible crew/equipment: When the passerby drops his lit cigarette in Phoebe's charity bucket, the end of the department store facade can be seen at the left side of the screen, and later when Phoebe hands off the bell to her replacement the end of the right side facade can be seen as well.
Visible crew/equipment: While everyone's in the apartment Ross is on the balcony talking to Emily on the phone, and in the mirror we can see the reflections of Phoebe and someone else wearing a blue shirt (with a large white pattern) and blue pants (looks like jeans), but none of the others are actually dressed like that.
Visible crew/equipment: Just as Monica and Rachel walk into the storage room, at the start of the shot the camera casts a shadow on the head sculpture which moves as the camera moves.
The One With The Racecar Bed - S3-E7
Visible crew/equipment: While Rachel and Ross are at the apartment, Rachel tries to convince Ross to have brunch with her father so they can get along, and in the shots facing Rachel we can see the movement of a crew member in the window's reflection.
The One With Frank Jr. - S3-E5
Visible crew/equipment: After Joey nearly drills a hole into Chandler he heads over to Monica's to get a beer, and just as Joey walks into the apartment the camera can be seen at the left side of the screen.
The One With The Metaphorical Tunnel - S3-E4
Visible crew/equipment: After Chandler gives Janice the contact paper for his dresser drawer, when Chandler stands up and says, "Yes, I did," we can see the camera at the right side of the screen.
The One In Barbados, part 2 - S9-E24
Visible crew/equipment: During Monica and Mike's game, after Mike makes the comment that Monica should look in the mirror before calling herself a girl, in the following wideshot after the closeups the camera/equipment can be seen at the right side of the screen.
The One With Rachel's Dream - S9-E19
Visible crew/equipment: After Monica and Phoebe apologize to each other at Javu, when it cuts to Rachel walking into the apartment we can see part of the hole in the wall beside the bulletin board, and the light fixture above it is gone.
The One With Rachel's Other Sister - S9-E8
Continuity mistake: When Rachel tells Amy that she'll let her use the Ralph Lauren discount Amy hugs her, and the glass Amy's holding in her left hand switches to her right hand and then back to her left hand, between shots.
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.