Continuity mistake: When Ross and Rachel are pushing Emma on the swing, the legs of Emma's pants change position several times between shots. At first they are pulled up with her legs exposed, then they are down further, and in the last shot when Ross gets kicked, they are pulled up again.
Revealing mistake: When Monica leaves her apartment in the scene where she thanks Chandler for staying calm since they got engaged you can see the wall on the left side of the door moving as the door closes.
Continuity mistake: When Chandler and Phoebe go to the jewelry store Phoebe's hair has two braids on each side that are being held together by what appears to be a hair pin, later on the scene where Phoebe is trying on a tiara she only has one braid on each side and no hair pins.
Continuity mistake: When Phoebe is talking to her stalker for the first time, at one point, he tips the flowers to the side when Phoebe says, 'Well, this is awkward,' and he puts his left hand on the end of the stems. In the next shot he is holding them with both hands.
Other mistake: There are two mistakes in the scene where Phoebe spots Joey's picture in the laundromat. For one thing, when Phoebe says "Oh, here it is", she is looking in the opposite direction of the picture. Also, when she says this, her mouth doesn't move at all.