The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: When Rachel gets back from shopping, all the stage lights can be seen in the tv. (00:11:50)
The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: When Rachel exits her bedroom and says she's going to London, you can see tape markings on the floor by her bedroom door and the end of the set. Furthermore, you can see a chair which is likely part of the Central Perk set. [Widescreen version]. (00:20:25)
The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: At the start of the first exterior shot of the London Marriott Hotel, when the camera pans to the left and reaches the awning the reflection of the camera/crane can be seen, and we also see it turn and lower.
The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: After Ross and Monica talk about Emily's dream of the perfect wedding and perfect guy (and Monica's pillowcase), when it cuts to Phoebe and Rachel at the apartment we can see a crew member (wearing a blue shirt) at the left side of the screen, before Phoebe mentions that she thought of a good flaw. (DVD).
The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: When Joey, wearing the Union Jack hat, walks into the hotel room while Chandler's sitting on the bed, on the widescreen version we can see the end of the set wall at the right side of the screen. On the DVD, just as Joey walks across the room studio lighting can be seen at the top left side of the screen.
The One With Ross's Wedding, part 1 - S4-E23
Visible crew/equipment: When Rachel opens the door to the apartment while she's holding flowers and sees Phoebe trying to get up from the couch (before the wedgie comment), the open edge of the set wall can be seen at the top left corner of the screen.
The One With All The Kissing - S5-E2
Visible crew/equipment: When Rachel tells her date she's going to have to take a rain check and goes back into the apartment, as she opens the door you can see a cameraman standing inside the apartment. (This is only visible in the broadcast version, not DVD or widescreen). (00:10:45)
The One With All The Kissing - S5-E2
Visible crew/equipment: When Rachel is telling Monica, Chandler and Phoebe how Ross abandoned her at the airport, when she walks towards the TV a boom mic is briefly visible at the top left of the screen.
The One With The Triplets - S5-E3
Visible crew/equipment: In the scene with Joey filming Phoebe and Phoebe saying, "Please don't hurt me," Joey zooms out and you can see the camera that is just about to film them. (00:00:35)
Visible crew/equipment: When Ross notices that Ugly Naked Guy is back, in the next exterior shot we can see the top of the set as everyone gathers at the window.
Visible crew/equipment: While everyone's in the apartment Ross is on the balcony talking to Emily on the phone, and in the mirror we can see the reflections of Phoebe and someone else wearing a blue shirt (with a large white pattern) and blue pants (looks like jeans), but none of the others are actually dressed like that.
Visible crew/equipment: Just as Monica and Rachel walk into the storage room, at the start of the shot the camera casts a shadow on the head sculpture which moves as the camera moves.
The One With All The Thanksgivings - S5-E8
Visible crew/equipment: Monica is explaining her Thanksgiving to Chandler; when she drops the knife there is a shot looking up from the floor. A crew member's shadow is visible on the ceiling. (00:07:10)
The One With All The Thanksgivings - S5-E8
Visible crew/equipment: Just as Monica finishes her story and Chandler is shown, the reflection of the stage lights is visible in the TV. (00:18:20)
The One With The Inappropriate Sister - S5-E10
Visible crew/equipment: At the start as Joey comes out, watch the tv and you will see a line of stage lights. (00:00:05)
The One With The Inappropriate Sister - S5-E10
Visible crew/equipment: When Ross and Monica are wrestling, the stagelights can be seen in the tv. (00:12:45)
The One With The Inappropriate Sister - S5-E10
Visible crew/equipment: When the passerby drops his lit cigarette in Phoebe's charity bucket, the end of the department store facade can be seen at the left side of the screen, and later when Phoebe hands off the bell to her replacement the end of the right side facade can be seen as well.
The One With All The Resolutions - S5-E11
Visible crew/equipment: Monica and Chandler leave the apartment to go "do laundry," then Phoebe heads out to the airport. When Joey takes a seat, the reflection of camera movement is visible on the window, above the sink. Then Rachel and Joey tell each other they can't share what they each know, and just as Rachel sits down beside Joey, once again we can see the reflection of camera movement above the sink. (00:19:30 - 00:20:20)
The One With All The Resolutions - S5-E11
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.
The One With Chandler's Work Laugh - S5-E12
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).
Answer: Usually by the seventh night of Hanukkah you don't know what to get the other person, and you will probably resort to getting the other person something insignificant. Chandler is basically saying that the pen is a stupid gift.