Revealing mistake: At the end of this episode when Carrie is walking away from Mr. Big's apartment; she notices an Autumn leaf, and follows it with her eyes as it floats down to the ground. However, this leaf is actually digital and not real. Sarah Jessica Parker had to pretend to be staring at a leaf that wasn't there while filming; and if you watch her gaze carefully, it doesn't always follow the path of the leaf. She looks down too soon, before the leaf has a chance to float down that far.
Revealing mistake: Just after Big has left NY for good, Carrie leaves his apartment and is walking down the street. A leaf (that another mistake pointed out was digital as it was falling to the ground) is lying on the sidewalk. Carrie picks it up, but it is obviously an artificial one made from plastic and fabric.