Visible crew/equipment: After Joey and Phoebe place their betting cash on the counter, when Joey says, "Let's get the contestants out of their isolation booths," the end of the set wall can be seen behind the foosball table. (Widescreen version).
Visible crew/equipment: After the anniversary party, when Rachel and Ross are back at the apartment and Ross tells her that it was the easiest four hundred bucks he ever made, Rachel gets up and just as she walks around the couch we can see the reflection of the cameraman/crew member in the mirror on the wall, at the right side of the screen.
Visible crew/equipment: After Monica and Chandler leave the apartment so Joey and Rachel can be alone, Rachel tells Joey that it's nothing and he tells her he's going to take-off, then in the next wideshot the camera can be seen at the left side of the screen.
Visible crew/equipment: When Ross is wearing roller-blades while teaching his class, just as he points to the map and says, "Here," the second time, there's a hidden crew member that can be seen behind the end of the set wall with the map, at the left side of the screen.
Visible crew/equipment: While Phoebe and Tim are at Central Perk, when Tim's beeper goes off he blows Phoebe a kiss when he leaves, and as Phoebe catches that kiss and throws it away have a look at the left side of the screen, where the Central Perk wall ends we can see part of Monica's restaurant kitchen set - the door and the wall beside it. (Widescreen version).
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.
Visible crew/equipment: After Rachel puts the videotape in the VCR, when she uses the remote to hit play it cuts to a closeup of the TV, and before the tape starts playing we can see the reflection of the camera dolly and a crew member wearing a white shirt, kneeling on the floor.
Visible crew/equipment: After Monica asks Rachel if there's someone else and shouts, "Why the hell are you dumping my brother?," when it cuts to Chandler sitting at the counter, the edge of the set can be seen at the left side of the screen, and also note the front door is wide open for the camera access. Additionally, when Joey joins Chandler at the counter the juice box has black tape covering its brand name.
Visible crew/equipment: After Rachel gets the call that she did not get the job, when she places the five dollar bet and asks if anyone has a problem with that, in the next wideshot as everyone says, "NO!" the reflection of moving equipment can be seen in the window behind Monica.
Revealing mistake: After Mr. Heckles has been taken away, in the last wideshot while everyone's still standing in the hallway, when this is viewed on the DVD (Warner Bros. S2 set) we can see a long black line on the floor (as noted in another mistake). The problem is that when this is viewed online on Netflix, even though we can see the very same area of floor, that black line has been blurred out. Weird that it wasn't edited on the DVD, and yet it was for the version available on Netflix.
Visible crew/equipment: After his fiasco with the leather pants, powder, and lotion, when Ross is at Monica's and tells the others he's going to kiss Ben goodnight, as he starts walking to the bedroom the camera can be seen at the right side of the screen.
Continuity mistake: After Joey makes up the story about how he slept with Monica once in London, in the shots facing Phoebe, Rachel, and Ross the door to Monica's apartment goes back and forth being either wide open or closed, depending on the angle of the shot.
Factual error: The restaurant refuses to take anyone's orders until they're all seated, which means that the group is sitting, occupying a table, without earning any revenue for the restaurant. There isn't a restaurant in NYC that would have such a policy, since it basically guarantees that a table becomes a revenue vacuum. (It also makes for very unhappy customers, but that doesn't qualify it as a factual error, since some restaurants might be actually stupid enough to not care about their return customers).
Visible crew/equipment: After the opening credits, just as Joey says that it's unbelievable Phoebe can be married, a camera and yellow electrical cord can be seen at the left side of the screen, and a bit of it is still visible in following shots when Monica mentions the cheeseburger.