The One Where Underdog Gets Away - S1-E9
Visible crew/equipment: When Joey walks into Central Perk and everyone's laughing about the VD ads, just as Phoebe comments that laughing can be "infectious" we can see the camera at the right side of the screen.
The One Where Underdog Gets Away - S1-E9
Revealing mistake: Whenever Monica's apartment is shot from the point of view of the balcony looking in, fake walls have to be put up across the room to cover the open space (since there is no wall there usually). When the friends are looking out the window at Ugly Naked Guy and his girlfriend in this episode, you can see that the rear wall does not extend nearly far enough - there is a large black space behind Monica. (00:19:25)
The One Where Underdog Gets Away - S1-E9
Continuity mistake: When Rachel gets her mail off Monica she puts it down on the couch and picks up a sealed envelope. The camera cuts and the envelope is now open with no time to open it. (00:07:25)
The One Where Underdog Gets Away - S1-E9
Visible crew/equipment: When Monica shuts the TV off while watching skiing, there is a closeup of the screen as it goes blank. You can see reflected in the blank screen an image of a man in a long sleeved shirt and tie, who does not correspond to any of the characters in the room. (00:08:00)
The One Where Underdog Gets Away - S1-E9
Continuity mistake: At the end of the episode when Chandler makes a toast, he is holding the glass in his right hand. In the next shot, the glass has jumped to his left hand. (00:21:05)
Suggested correction: He switches the glass from right to left, so, unfortunately you're wrong.
The mistake is valid. While we do see him switching his glass between hands during the scene, when he says he's glad everyone's Thanksgiving sucked, he raises his glass in his right hand. In the next shot it's switched to his left and lowered a bit. Since this happens between shots (and he's not off camera), it means no time elapsed, so there's no time for him to switch hands again (in the submitted pictures, the bottom picture is the first shot and the top picture is the 2nd shot).
The One Where Underdog Gets Away - S1-E9
Continuity mistake: When Rachel turns up with her tickets, Chandler has his hand on his hip. As Rachel walks off however, his arm is behind her. (00:12:00)
The One Where Underdog Gets Away - S1-E9
Visible crew/equipment: When Joey walks into Central Perk after the VD poster montage, a tape marker is visible on the floor behind Chandlers spot on the sofa. (00:10:40)