The One With The 'Cuffs - S4-E3
Visible crew/equipment: At the end, when Rachel walks into Joanna's office to find her handcuffed to the chair, the camera can be seen in front of the filing cabinet, at the right side of the screen.
The One With The Free Porn - S4-E17
Visible crew/equipment: After Emily says thank you to Ross and leaves, when it cuts to Chandler and Joey's apartment Rachel puts a tea bag in her mug, and in the wideshot as she says, "He told me," the camera can be seen at the left side of the screen.
The One With The Free Porn - S4-E17
Visible crew/equipment: After Joey asks Ross to buy him a Toblerone just as Ross heads out to the airport, when it cuts to the shot of Rachel and Phoebe walking into the apartment, the camera can be seen at the right side of the screen.
Visible crew/equipment: When Chandler points out to Joey that his oblivious comment was made in front of Ross it cuts to a closeup of Ross, and camera equipment can be seen at the right side of the screen, and it's still there in the next two closeups of Ross.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: While Joey's looking for the "hot girl" the second time, after he knocks on the little girl's door and asks if her mother, sister, or babysitter are a hot girl, he runs off when she shouts for her father, and when Joey stops in another hallway full of doors the shadow of the moving boom mic can be seen on the door beside him.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: When Rachel gets back from her first interview, just as Chandler says, "Oh hey," we can see the boom mic at the top of the screen.
The One With Rachel's Inadvertent Kiss - S5-E17
Visible crew/equipment: When Joey is standing at Monica's window waving to Ross, the end of the set wall with movement on the soundstage can be seen at the left side of the screen.
The One Where Everybody Finds Out - S5-E14
Visible crew/equipment: When Ross is using the binoculars to watch Ugly Naked Guy's apartment, the end of the set wall can be seen behind him.
The One Where Everybody Finds Out - S5-E14
Visible crew/equipment: When everyone's looking out Monica's window into Ugly Naked Guy's apartment, and see all the gift baskets he's been sent, the end of the set wall in Monica's apartment can be seen.
The One Where Everybody Finds Out - S5-E14
Visible crew/equipment: While Phoebe and Rachel are at Ugly Naked Guy's apartment, when Phoebe looks out the window and sees Monica and Chandler the end of the set wall in Monica's apartment can be seen.
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.
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 The Racecar Bed - S3-E7
Visible crew/equipment: While Rachel and Ross are at the apartment, Rachel tries to convince Ross to have brunch with her father so they can get along, and in the shots facing Rachel we can see the movement of a crew member in the window's reflection.
The One With Frank Jr. - S3-E5
Visible crew/equipment: After Joey nearly drills a hole into Chandler he heads over to Monica's to get a beer, and just as Joey walks into the apartment the camera can be seen at the left side of the screen.
The One With The Metaphorical Tunnel - S3-E4
Visible crew/equipment: After Chandler gives Janice the contact paper for his dresser drawer, when Chandler stands up and says, "Yes, I did," we can see the camera at the right side of the screen.
The One With Rachel's Dream - S9-E19
Visible crew/equipment: After Monica and Phoebe apologize to each other at Javu, when it cuts to Rachel walking into the apartment we can see part of the hole in the wall beside the bulletin board, and the light fixture above it is gone.
The One With The Cooking Class - S8-E21
Visible crew/equipment: When Joey and Monica are leaving the cooking class, the teacher asks about the difference between hollandaise and béarnaise sauce, and in the next shot of Monica and Joey we can see the shadow of the moving boom mic at the top left side of the screen.
The One with All the Poker - S1-E18
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.
The One Where Heckles Dies - S2-E3
Visible crew/equipment: When Mr. Heckles is being taken away, just as the officer starts to follow the gurney the shadow of the moving boom mic can be seen on the wall behind him, at the right side of the screen. (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.