The One With The Girl Who Hits Joey - S5-E15
Other mistake: When Ross and Phoebe are eating cheese puffs and party mix out of the bags, Phoebe's bag reads "Heez-I" instead of Cheez-It, and the brand "Sunshine" has been covered.
The One In Vegas, Part 1 - S5-E23
Visible crew/equipment: When Ross is leaving Rachel's, a stagelight can be seen by the bathroom. (00:12:00)
The One With Joey's Bag - S5-E13
Visible crew/equipment: When Joey walks into Monica's apartment the first time, a stage light can be seen by the window near the bathroom. (00:10:00)
The One With All The Kissing - S5-E2
Factual error: When Monica is in the bath with Chandler, Joey comes in twice, forcing Monica to hide under the bubbles: first he asks Chandler if he wants some chicken, then again when Chandler calls him back and Chandler's giving Monica's order, with Monica still hidden under the bubbles. Somehow, Monica supposedly hears Chandler requesting a soda and nudges or pulls him or something to indicate he was going to get the wrong kind. But no way she could hear him under the water (stick your head in a tub and have your friend recite the alphabet, and see what I mean). (00:01:00)
Other mistake: When Ross tells Rachel he can't see her anymore, the door to Monica's room is open revealing a completely blank and empty room. (00:09:50)
The One With Joey's Big Break - S5-E22
Continuity mistake: When Rachel knocks over the cereal its position changes between shots. (00:04:15)
The One Where Everybody Finds Out - S5-E14
Visible crew/equipment: When Rachel stands up to get laundry for Monica, a stage light can be seen in the TV. (00:07:20)
The One With The Girl Who Hits Joey - S5-E15
Continuity mistake: The frosting on Ross's mouth changes between when someone says "who cut Howard's cake" and "3b". (00:16:00)
The One With All The Resolutions - S5-E11
Continuity mistake: During the countdown to midnight, just as everyone says, "Happy New Year!", the camera cuts to Phoebe and Ross. In the background Joey and Rachel open their arms to hug each other; the camera cuts to just Joey and Rachel and they open their arms again. (00:01:00)
The One Where Ross Can't Flirt - S5-E19
Continuity mistake: After Joey runs out of the apartment to go make the fake videotape, when it cuts to Rachel walking back into the apartment the table with the tablecloth is quite far away from the front door, but when Caitlin knocks and Ross rushes to go flirt with her that table is near the door. (00:13:35 - 00:15:15)
The One With Rachel's Inadvertent Kiss - S5-E17
Continuity mistake: While the two couples are at the restaurant, Chandler has a beer and Gary, Monica, and Phoebe have margaritas, and the amount of liquid in Gary's margarita glass keeps changing, back and forth from less to more.
The One With The Ride-Along - S5-E20
Continuity mistake: When Rachel is at Ross' apartment she gets the blender and while she's standing at the window talking to Monica on the phone the kitchen door is closed, then it's wide open, and then closed again.
The One With The Girl Who Hits Joey - S5-E15
Continuity mistake: When Phoebe gives the housewarming gifts to Ross and also when Ross opens the door for the neighbor, his apartment number is "3B" and his neighbor's door is "3A," but in episode 14, "The One Where Everybody Finds Out," the door can be seen three times during the episode, and the number is "201" each time.
The One With The Girl Who Hits Joey - S5-E15
Continuity mistake: When Ross tells Chandler and Rachel that he's running out to buy name tags for his party, in the next shot the water bottle beside Rachel does not have its cap on, but it cuts to Rachel's closeup and the cap is on. Other differences can be seen as well, such as Rachel's hair and an extra utensil.
The One Where Everybody Finds Out - S5-E14
Continuity mistake: When Phoebe pours the white wine Chandler empties his glass to the last drop, but in following shots Chandler's glass has wine again, which then keeps vanishing and reappearing.
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 Inappropriate Sister - S5-E10
Continuity mistake: Joey and Chandler are playing 'Fireball'; Joey puts his hand through the wall next to the fridge, then in the next scene the hole is gone with no trace. (00:08:50)
The One Where Ross Can't Flirt - S5-E19
Continuity mistake: When Phoebe asks Rachel for the earrings she borrowed, Chandler is visible in the background, standing up with one leg on the table and talking to Joey. When the camera angle switches, Chandler is sitting down. (00:05:00)
The One With The Triplets - S5-E3
Continuity mistake: When they enter the hospital, Phoebe says, "Someone should call Frank and Alice, and my mom," and Ross searches his pockets(presumably for his cell phone). But in the next shot, his hands are not in his pockets. (00:00:05)
The One With Rachel's Inadvertent Kiss - S5-E17
Factual error: When Joey tries to find the Hot Girl, he goes up to Ross' apartment and there is a dead end. However, when he next goes there, he manages to run away in that direction. (00:03:20)
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.