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.
Continuity mistake: When Monica comes in and asks Chandler if she can borrow some milk, Chandler is reading a paper that is flat on the bar. In the next shot he is holding it folded, then he lays it on the counter, and suddenly it is in his hands again.
Visible crew/equipment: Just after Chandler says "I'm the smallest person in the world", and Joey comes out of his room, check the top left of the screen - you can see a boom mic track Matt LeBlanc across the set, and the bottom of some stage lights in the middle.
Visible crew/equipment: When Monica and Chandler are discussing the date he had with Ginger, when he says, "She's great looking," two stage lights are visible in the background. This mistake is visible for a long period of time, where it's slightly visible, shown in shadows, and largely visible as Chandler and Monica are talking.