Continuity mistake: Carrie goes inside the changing booth to try on the pink outfit. Then after Stanford and Marcus arrive, Carrie suddenly whips the curtain open to reveal herself completely changed into the new outfit including shoes, after only 21 seconds. These events happen in real time; and there is no logical way that Carrie could have changed from one complete outfit to another in that time.
Revealing mistake: When Samantha is walking down a busy NYC street talking on her cell to Carrie, you can see a man in a blue jacket walking right behind her. The next shot of him; he suddenly pulls out an obvious black camera and takes a photo, aiming it directly at Samantha in front of him. This is apparently not an 'extra', but someone on the street who wanted to take a picture of Kim. There are also a lot of other people in the background walking behind her at this point. But in the next shot of Samantha still walking on the same street and talking on the phone, there are suddenly no people right behind her at all. It's an empty space, and no time has passed for them to have dispersed. They may have cleared the area behind her; because people weren't behaving properly during filming, such as the man taking her picture. This would normally be a continuity error; except that in this case I believe the sudden change in background was due to the guy taking the picture inappropriately, not just a slip in background filming.