When Phoebe is talking to the lady with the cigarette and telling her to apologize to the tree, her purse changes from one shot where it's above her coat to the next where it's under her coat.
When Phoebe's cover is blown and Gary asks, "And where'd you find my badge?", the word "badge" is dubbed in and does not match his lips.
When Ross, Chandler, & Rachel are moving the couch up the stairs, Rachel is heard saying " "Ross I just don't think it is going to fit." It is clear that Rachel's lips are not moving and the sound does not match.
Right after Ross says "that's my arm" and the camera angle changes to Rachel, Chandler, and Ross, you can see him saying "that's my arm" again but no sound is heard.