Continuity mistake: In the episode "Secret Sex," Samantha and Carrie are hanging Carrie's poster in her apartment. In one shot, the whole poster is pinned to the wall and in the next shot, the bottom left part of the poster is curling up. After another shot of Samantha, the poster is pinned perfectly to the wall again.
Plot hole: In this episode Carrie runs into Aidan, who now has what looks to be about a 6 month old baby (Tate). This doesn't seem possible, as Carrie and Aidan would have only broken up about a year ago, and Miranda was around 6 months pregnant when they broke up. Brady is only about 5 months old at this point in the series, leaving Aidan only roughly 8 months to have this baby - but Aidan lay in bed for about a month and then dated Nina Katz for awhile. Timeline just doesn't seem to fit.
Continuity mistake: When Samantha is talking to Carrie on the beach, Carrie lifts her arm up and places her hand on her head. The reflection on Samantha's glasses show Carrie lowering her arm, but the shot changes back to Carrie and the movement she is doing is not downwards but backwards, leading hear hand to the nape.
Continuity mistake: In the scene where Carrie and Miranda are eating cakes outside the shop, talking about Miranda having to be supportive to Steve about his basketball competition, keep an eye on Miranda's cake. She takes bites out of the cake and then when it is down to the last bite, the camera shows Carrie, then shows Miranda again with the cake suddenly full again.
Continuity mistake: In season 1 "Valley of the 20-Something Guys," Carrie receives a phone call from Samantha and her voice over says she needs her morning Marlboro Light, however, when she picks up her pack of cigarettes, you can see that it is a pack of Merits.
Other mistake: When Carrie, Samantha and Miranda step outside of the hotel so Carrie can have a cigarette, she takes a couple of draws then throws it down on the step. She tries to stub it out with her shoe by twisting her foot on it but she (the actress) accidentally kicks the cigarette down the step, so she has to just pretend to still be stubbing it out.
Continuity mistake: When Carrie is startled by the squirrel and tosses the pie crust onto the counter, the camera cuts to her clasping her legs where she burnt them. In the next shot of the counter the pie crust has vanished; then in the next shot of it, the crust has returned.
Continuity mistake: The episode 'Attack of the 5 foot 10 woman' in season three, when Charlotte is afraid of the sauna. She is running into the sauna with a towel wrapped around her waist. The towel comes loose and is nearly falling off - but in the next shot it is neatly tied around her waist.
Revealing mistake: When Charlotte is putting her diamond ring on in her apartment, there is a close-up shot of it. It is a large, circular diamond on a simple golden band. This is not the same diamond engagement ring she has been wearing previously in the series. That ring had two parallel silver bands, and the diamond looked slightly different.
Factual error: Throughout this episode, when Carrie talks about the functions of the left vs. right sides of the brain, she has them backwards. The right side of the brain is the creative side, the left is the logical one. Apparently, the writers liked the idea that the "right" side of Carrie's brain would ultimately lead her to do the "right" thing about Mr. Big, but that's not the case. Rational decision are made with the brain's left side. (But then again, Carrie never was very rational when it came to Mr. Big.).