10 More Annoying Mistakes You Never Noticed In Friends
9. Monica's Closet Of Shame
In "The One with the Messy Closet" in Season 8 Chandler obsesses about a locked door in Monica's apartment. He claims he's never seen what's behind the door while Joey throws out some wild guesses, showing that he hasn't seen what's inside either. Eventually Chandler manages to find out what's behind it, only to discover a small closet with a huge mess. The usually highly-organized Monica is so ashamed when she sees that Chandler has discovered her messy secret.
However, that same door has been left open in earlier episodes without anyone commenting on it. For example, in "The One with the Boobies" in Season 1 the door is open while the group is hanging out in the apartment. Inside it just looks like a normal and organized cupboard.