Trivia: The song lyrics that Joey sings during his production of Freud! are:
"All you want is a dingle.
What you envy's a schwang.
A thing through which you can tinkle,
Or play with, or simply let hang."
Goof: When Joey is filming the shower scene, he is supposed to be naked. However you can clearly see from his shadow that he is wearing shorts.
Trivia: In Phoebe's song, she says that she stays away from dairy. This hints that she's lactose intolerant or vegan.
Goof: When Rachel introduces Phoebe at Central Perk, Gunther is visible in the background even though his character has not yet been introduced.
Continuity: When Rachel and Phoebe go to Mr. Heckles' door, Phoebe doesn't seem to know who Heckles is, yet in "The One with The Flashback" he comes to Monica's door to complain and Phoebe knows exactly who he is, even calling him by name.
Factual Error: Ross told the gang that the weirdest place he's done it was at Disneyland and then he said he and Carol were asked to never return to the Magic Kingdom. However, The Magic Kingdom is part of Disneyworld in Florida, not Disneyland, which is in California.
Factual Error: During the blackout, Joey brings over what he refers to as a Hanukkah menorah. Ross makes a Rabbi joke, and Joey says Chandler's Jewish roommate left it. However, this is a Jewish temple menorah, not a Hanukkah menorah.
Factual Error: Joey says that the weirdest place he has ever had sex is the women's room on the second floor of the New York City Public Library. However, the bathrooms there are located only on the third floor.
Trivia: When Joey mumbles to Chandler on the phone, he says "See if you can tell what kind of underwear she wears."
New York City has no power,
And the milk is getting sour.
But to me it is not scary,
'Cause I stay away from dairy.
La la-la la-la la-la la...
Continuity: Ross says he and Carol were banned from Disneyland in 1989. But in "The One with Rachel's Assistant" we find out Ross visited Disneyland his junior year in college, which chronologically would have been after he was banned.
Trivia: Here are the translations for Paolo's lines in Italian.
Paolo is being introduced in Monica's apartment.
Paolo: Ragazzi, sono appena arrivato e vivo al piano di sotto, quindi ci vedremo molto spesso, penso.
Translation: Guys, I've just arrived and my apartment's downstairs, so I'll see you quite often, I think.
Paolo: Phoebe, anche tu bellissima. Se siete tutte così belle mi trasferisco proprio qui.
Translation: Phoebe, you're so beautiful too. If you girls are all so gorgeous I'll move right here.
Paolo and Rachel are looking outside.
Paolo: Guarda la luna, guarda le stelle... Guarda tutte le cose belle.
Translation: Look at the moon, look at the stars... Look at every beautiful thing.
Trivia: The ATM vestibule which Chandler was stuck in belongs to Emerson Bank, according to the title on the glass door.
Goof: When Ross falls in the open grave, there is a lot of mud visible on his knees when he rolls over on to his back. When the camera angle changes to the reactions of his friends and then back to him in the grave, there is no mud at all on his knees.
Continuity: Rachel says she thought Chandler might be gay when she first met him, but later dismissed the thought since he spent Phoebe's birthday looking at her breasts. Rachel met Chandler for the first time when she was still in high school and they actually made out at a party, as seen in "The One Where the Stripper Cries." So it's highly unlikely she didn't realize he was straight before Phoebe's birthday many years later.
Continuity: Joey says he didn't think Chandler was gay when they first met. In "The One with the Flashback", where they meet for the first time, Joey does think Chandler is gay.
Continuity: Phoebe's birthday is inconsistent. In "The One with Frank Jr." Phoebe tells her half-brother that her birthday is February 16th. Also, in "The One with Two Parts (2)" Phoebe has a birthday party in February. However, in this episode, Rachel talks about Phoebe's last birthday party. Since Rachel first met Phoebe earlier that season, this implies that Phoebe's birthday must have occurred since September, when Rachel first joined the group. Also, in "The One with Phoebe's Birthday Dinner", Phoebe's birthday is close to Halloween, consistent with Rachel's statement. Furthermore, in "The One Where They All Turn Thirty", the flashbacks of Phoebe's 30th (really 31st) birthday imply her birthday is in the summer.
Trivia: Although Phoebe's job as a masseuse still hasn't been mentioned, we see her checking out Ross's back spasms after he falls. In the pilot episode, she also offers to massage Monica's feet, but you wouldn't necessarily have to be a masseuse for that.
Trivia: This episode is the first one to joke about Chandler's gay mannerisms or "quality". This became a running joke throughout the series. The role of Chandler was originally going to be gay, but the idea was scrapped after Matthew Perry was cast.
Continuity: Phoebe says that Ugly Naked Guy is pulling his turkey out of the oven. However, in future episodes when Ross moves into that apartment, the kitchen is behind a door and is not visible from Monica's apartment.
Note: In many shots of Ross's apartment as seen from Monica's window, the kitchen door is visible, such as in "The One with Rachel's Sister". It's entirely possible that the kitchen door would be open when Ugly Naked Guy is taking his turkey out of the oven.