Continuity mistake: In the One in Barbados (part 2), just after Monica bashes her hand against the table, the shot of Chandler asking if she's OK shows Monica raising a finger right at the edge of the screen. We then cut to Monica, who's cradling both her hands together.
Continuity mistake: When Chandler, Joey and Monica tell their story of the jellyfish bite Chandler says sometimes at night he still hears Joey's voice screaming "Do it ! Do it!". Joey says he yells it through the wall at night to freak Chandler out, but no nights have passed. They tell the story the same day the jellyfish bite occurred. Notice Rachel, Ross and Phoebe are wearing the same clothes they had before they left the beach house.
Continuity mistake: In the scene where Rachel believes Joey has proposed to her at the hospital after having Emma. Ross is talking to Rachel about her saying yes to Joey's proposal. The nurse brings Emma in to breast feed. When the nurse leaves, she closes the door. However, when they shoot back to Joey a couple of times before he leaves the room, the door is open.
Visible crew/equipment: When Rachel is on the balcony with her date, after she kisses Ross and says, "Wow!", the shot changes back to her date. While he is saying, "Exactly" you can see a camera man on the left side of the screen. Then when the shot changes to show Rachel and her date you can see him move out of the shot.
Continuity mistake: When Joey is telling his story about throwing Ginger's wooden leg in the fire, when he gets to the part about him, Ginger and the dog Pepper falling asleep in front of the fire, a large section of her hair falls in front of Phoebe's face. In the next shot it's gone;, however her hands are visible the whole time and she has not pushed the hair back.
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.
Continuity mistake: At the end of this episode, Ross opens the door of Rachel's room, says "Hi", and then closes it. However, in the next episode (The One With The Jellyfish), this scene is shown again and changed: Ross opens the door of Rachel's room, says "Hi", and doesn't close it - he talks with Rachel and Bonnie with the door open.