Continuity mistake: Towards the end of the episode, Ross and Chandler come into Monica's apartment and Ross asks where Rachel is. Watch the objects in Monica's hands, in the shot from behind she puts them on the table, and then does it again in the shot from the front.
Continuity mistake: When Ross and Chandler are talking about who broke which pact in college (the girls they agreed not to date) they are standing at the drinks table. Chandler is holding a drink in his left hand and his right hand is in his pants pocket. The shot then changes to face Ross, Chandler does not remove his hand from his pocket, but in the next shot facing him his drink is in his right hand. He then places it on the table.
Continuity mistake: When the girls and Mr Goodbody are talking about paying him the three hundred dollars, the top buttons of his shirt are ripped open. Half way though the scene this changes to only one button being open and his shirt looking neat and pressed, as if he had not started his strip yet.