Plot hole: The times in this episode vary a lot. Monica and Phoebe first bet about Rachel giving birth, then it goes to the scene with Joey and Chandler at the movies. It then returns to Monica and Phoebe the next day with Monica losing the bet. However, a little while later, it goes back a day and shows Joey and Chandler at the movie premiere again.
Other mistake: When Joey and Chandler and in the cab on the bridge, Joey quickly stops the cab so Chandler can get out. However, on the screen behind, the background doesn't 'slow down' as Joey does, it just continues as if the cab is going at the same speed. Then, in the next shot, it is still. When Joey sets off again, the background stays the same and doesn't show that the cab is getting faster.
Continuity mistake: As Chandler meets Monica at the altar, Monica's hand switches from holding Chandler's hand, to holding the flowers, with no time to do so.
Other mistake: When Chandler says "We just got married. Right there!" and points. We hear a small 'ding' and Monica asks "Is that your ring?" But when Chandler pointed, you can see that all of his fingers except his index finger are closed to his hand. So the ring couldn't have come off.