Continuity mistake: When Chandler throws his copy of "Chicken Soup for the Soul" under the sofa and it goes across the floor to Monica's feet, she kneels down to pick it up by the counter next to the door, but when she rises, she's next to a chair that's under the table.
Continuity mistake: Jill goes to Ross' place, intending to make Rachel mad. When Ross goes to Rachel's to talk to her afterward, she rolls up her sleeves saying, "I'll give you something to think about." When Rachel is next shown, her sleeves are rolled down. Her arms also go from by her sides to crossed in front of her.
Continuity mistake: In the beginning of the episode when Joey tells Chandler that he hasn't forgiven him for kissing one of his sisters, Monica and Chandler's TV, entertainment set and ferns are missing from the set and there are cables protruding from the wall. The area is completely bare except for the French poster. Everything's back to normal slightly later in the episode.