Revealing mistake: When Carrie bumps into Mr. Big and her purse falls, watch the people in the background carefully. Many of them are watching the couple talk and interact with each other. On a busy New York street nobody is going to pay attention to two people having a conversation. Apparently all these people were watching the shooting of the scene.
Revealing mistake: When Abby and Jen are drinking on the dock, Abby suddenly falls into the ocean and drowns. Just as they show a close-up of Abby falling about to hit the water, you can tell it's a stunt person. Monica Keena is a fairly short actress, and the stunt person is noticably taller with longer legs. Also, Abby had been wearing a very decorated black and silver skirt while on the dock. But the person about to hit the water appears to be wearing dark clothing without any silver or glitter.
Revealing mistake: When the van drives upstairs, you can see that it wasn't destroyed.
Revealing mistake: When Rachel and Adam first meet, their cars crash in the car park. In the shot where they both get out of their cars, you can see a dry patch of ground under Rachel's car, but the rest of the area is wet. Why would that space be dry, if Rachel just crashed and it isn't raining heavily at the time?
Revealing mistake: There's a stunt featuring two-way too obvious body doubles for Kelly Hu and Gretchen Egolf rolling over a table; not only the stunt itself is rather underwhelming and blatant, but also the objects on the table disappear just so the two can perform it.