The One With Ross's Inappropriate Song - S9-E7
Visible crew/equipment: When Monica comes home at the end, as Joey pulls her down on top of Chandler as to protect her eyes from seeing the tape, you can see a knee pad on Courteney Cox's knee, under her skirt. (00:14:20)
The One With Ross's Inappropriate Song - S9-E7
Visible crew/equipment: While Chandler and Joey are watching Richard's videotape, when Chandler's relieved it's just football he heads off to get beer, and in the next shot as he hears the sound of moaning we can see the opening in the wall behind the TV.
The One With Ross's Inappropriate Song - S9-E7
Visible crew/equipment: When Joey jumps on Chandler to shield him from seeing Monica's sex tape, the mat they land on is visible prior to the scene.
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.