Revealing mistake: In the scene in the coffee house, Phoebe is talking to Monica who is drinking a cup of coffee. Towards the end of the scene, the camera is on Phoebe who is smiling & laughing at Monica. In the right hand corner is a side view of 'Monica' however, it is not Courtney Cox in the scene, but a completely different actress. [Widescreen version only, although the "wrong" nose is visible in the original]. (00:06:20)
Visible crew/equipment: After Ross and Rachel cover the table with the sheet, when Phoebe walks in Rachel says they can turn out the lights and watch the movie, and in the next shot we can see the end of the set wall, the soundstage and a crewmember's leg.
Visible crew/equipment: When Ross shows up at Chandler's office and they both head out to go to the Hard Rock Cafe, just as Chandler walks out the door we can see the edge of the right wall set, allowing us to see the hallway Chandler just walked into and even Chandler's arm.
Continuity mistake: When Rachel finds out that Ross and Julie are getting a cat, watch Rachel's neck. When she says "together?" she's not wearing a necklace; cut to Ross and Julie for a fraction of a second, then when it cuts back to Rachel saying "both of you?" she's suddenly wearing a necklace. It then disappears again when she says "isn't that just lovely?" hanging off the side of the tray she's holding. (00:05:15)
Visible crew/equipment: While Phoebe and Rachel are with Monica in the guestroom, Phoebe decides that Rachel should be the one to get the nice room, and right before Monica tells Rachel that she's the first guest at "Hotel Monica" we can see the end of the bedroom set wall, with the kitchen and living room visible.
Other mistake: When Phoebe and Ross are at JFK, some of the people who are at that airport are the same people who are also at Newark. It's particularly funny to see the people behind Ross and Phoebe at JFK when Phoebe claims they're on their honeymoon, and when it cuts to Rachel at Newark as she's looking for her boarding pass, those same people are there too.
Visible crew/equipment: When Joey's telling Phoebe about having been at a nice restaurant with his date and how she took fries off his plate, in the shots facing Joey in the restaurant we can see the end of the set wall, with a 2x4 framed plywood board and a heavy duty extension cord hanging there.
Visible crew/equipment: When Joey's in the kitchen holding a football waiting for Janine to come home, so he can talk to her about getting rid of the girly stuff, just as Janine walks into the apartment the camera can be seen at the right side of the screen.
Visible crew/equipment: When Phoebe bends over to tie her shoelace before the first run, and later when she surprises Rachel at the park while running, the mic pack bulge under Phoebe's top can be seen on her back, and when Rachel bends over there's a bulge at her back as well. It's also a bit noticeable the third time they run.
Visible crew/equipment: When Phoebe tells Chandler that Monica wants to make up and that he needs to find her, when Chandler leaves the room we can see the end of the set wall, with the hallway and another hotel room door, at the left side of the screen.
Visible crew/equipment: When Monica walks into the apartment and announces to Chandler that they're not friends with Phoebe anymore, the hole in the wall beside the door (which is usually hidden behind the picture) can be seen when she walks in and also when Phoebe and Amanda walk in.
Visible crew/equipment: At the end of the scene where Ross buys the group gas at the rest stop, as the shot moves out on Ross leaning against Carol's car you can see the cameraman (and his camera) to the left of the screen. [Widescreen HD version only] (00:19:35)
Visible crew/equipment: After Ross goes in for his disastrous tan, when it cuts to Joey and Rachel walking into their apartment the hole (used for a camera angle) in the wall can be seen at the right side of the screen. As an aside, when Ross leaves Monica and Chandler's apartment later just as Rachel walks in, that hole is seen in the hallway and it's covered up.
Continuity mistake: When Joey is counting the floors of Ross' building (the first time) to find out where Hot Girl lives, he is wearing a black top with a zip. When he rushes over to Ross' building he walks down the hall and knocks on what he believes to be Hot Girl's door. In these shots he is wearing a dark purple button up shirt. As soon as Ross answers the door, Joey is wearing the black top with a zip again. (00:03:15)
Continuity mistake: When Joey goes to Monica and Chandler's apartment, he goes to the fridge to get something to drink to keep his bladder full for the audition. When he closes the fridge he has two bottles in his left hand. The camera cuts to Monica, then cuts back to Joey. He then has two cans in his left hand and is holding them differently. (00:14:55)
Visible crew/equipment: At the start, when Chandler and Joey sink into their new Barcaloungers and proceed to recline, the camera can be seen at the right side of the screen. This can also be seen in the show's intro in later episodes. Additionally, set lighting was reflected on the TV screen earlier when Chandler had mentioned "Green Acres."
Visible crew/equipment: After Rachel tells the others that her father had a heart attack and Ross takes two of Monica's cookies, when it cuts to the shot of Central Perk it's from a low angle, and the studio lighting rigs at the ceiling can be seen through the windows.