Other mistake: In his apartment from later episodes, Ross' kitchen door is on the same wall as the front door, and it is a long and narrow kitchen, but Ross' apartment is between two others. The floor plan doesn't make sense unless the kitchen is only a foot wide, otherwise it would jut off into the hallway.
Other mistake: Mid episode when Monica turns off the cordless phone after being told by Wendy that she can not make it, the phone makes the "out of range" audio tone instead of the "power off" audio tone. Occurs directly as Monica says, "Wendy, we had a deal, yeah, you promised. Wendy, Wendy, Wendy.".Wes
Other mistake: When Phoebe makes fun of Ross' Princess Leia fantasy with the rolls, Rachel tries to stop her; the shots used are the same action, just from different angles. Look at Rachel's hands and the towel in her hand when Phoebe puts the rolls by her ears.
Other mistake: In "TOW the cheap wedding dress" the whole episode is about how Chandler wants "The Swing Kings" to play at the wedding, because, at their concert, that is where he realised that Monica was the woman he wanted to dance all his dances with, and Monica goes to great lengths to secure the band. In this episode, the band at the wedding is actually called "Jungle Swing".
Other mistake: When Emily first walks in wearing her wedding dress, there is a distinctive difference between that dress and the one Monica picked up from the store a few episodes earlier and tried on (yes, more than that she is also wearing a jacket). There is a band of material at the top of the dress when Emily is wearing it that was not there when Monica wore it.
Other mistake: When Ross first goes out to play rugby and goes into the scrum, just after Emily talks to the rest of the players, he jumps into the middle of the scrum where the ball should be. Instead, in the next shot, the rugby ball is to the far left of the shot, not in the actual scrum.