The One With The Jellyfish - S4-E1
Continuity mistake: When Chandler, Joey and Monica tell their story of the jellyfish bite Chandler says sometimes at night he still hears Joey's voice screaming "Do it ! Do it!". Joey says he yells it through the wall at night to freak Chandler out, but no nights have passed. They tell the story the same day the jellyfish bite occurred. Notice Rachel, Ross and Phoebe are wearing the same clothes they had before they left the beach house. (00:16:20)
The One With The Jellyfish - S4-E1
Continuity mistake: Phoebe and her mother are in her mother's house at the beach. Phoebe has just found out that Phoebe senior is her real mother. Have a look at Phoebe's mother in this episode and the last episode of series 3 (The One At The Beach). Her hair is a lot shorter in series 4 even though no time has passed in the storyline. (00:03:35)
The One With The Jellyfish - S4-E1
Audio problem: When Phoebe is knocking on her sister Ursula's door to tell her about finding her birth mom, the third knock is heard a split second before you see Phoebe's hand action. (00:12:15)
The One With The Jellyfish - S4-E1
Visible crew/equipment: When Ross storms out of the room and the rest of the friends are in the kitchen, you can see the stage lights at the top of the screen. (00:20:15)
The One With The Jellyfish - S4-E1
Other mistake: When Chandler and Monica are sitting at the table after playing Gin, Chandler's bottle of Yoo-hoo is on the table, but the label reads "Yooh" because the brand name has been partially covered - the blue letters "oo" are yellow to match the background.
The One With The Jellyfish - S4-E1
Continuity mistake: When Monica gets stung by the jellyfish they are standing on a part of the beach that is wet and close to the surf but when she is saying "damn the jellyfish" the part they are standing on is dry and further from the water.
The One With The Jellyfish - S4-E1
Continuity mistake: In the last few seconds of season 3, Ross closes the door immediately after he steps through it. However, in the opening seconds of season 4, we see this same event from the other side of the door. This time however, Ross doesn't close the door for at least 15-20 seconds after entering the room.
Answer: The painting doesn't have a name, and if it does it is never mentioned in this episode.