The agony and the 'ex'tasy - S4-E1
Continuity mistake: When Carrie is showering after being stood up at her party she is not wearing mascara as she stands with her face under the water, then as she opens the curtain to talk to Charlotte again there is no mascara. She puts her hands briefly over her eyes and when she takes them away, mascara is visible all over her eyes and cheeks.
The agony and the 'ex'tasy - S4-E1
Plot hole: In the closing scene in Big's car, he asks Carrie how her birthday was, then says, "So how old are you?" She replies, "How old are you?" And they coyly don't reveal their "age box." But they have known each other for 3 years/seasons at this point - dated on/off for 2 years, had an affair, and are just friends now. There is no way they wouldn't know each other's ages. This exchange only existed to benefit the plot of this episode - it makes no sense given how long they've known each other.
The agony and the 'ex'tasy - S4-E1
Continuity mistake: When Miranda bumps into Cheryl on the street, she holds out her arm and starts shaking it like she is shaking Cheryl's hand but when the shot changes to Cheryl, she hasn't even taken Miranda's hand yet.
The agony and the 'ex'tasy - S4-E1
Revealing mistake: When Charlotte arrives at Carrie's apartment to pick her up, Carrie is in the shower. As Charlotte walks towards the bathroom, there is a clear shot of Carrie showering. Sarah Jessica Parker appears to be wearing some sort of minimal tan colored undergarments, to protect her modesty while filming. (00:24:20)
The agony and the 'ex'tasy - S4-E1
Continuity mistake: When Carrie holds the "Dear single" letter, the envelope is below the paper, but in the close-up it's behind the upper part of the letter.
The agony and the 'ex'tasy - S4-E1
Continuity mistake: Charlotte holds her notepad while Trey asks her to take off her panties. Then the notebook swaps hands.
The agony and the 'ex'tasy - S4-E1
Continuity mistake: Carrie grabs the "Two souls" invitation with her right hand, but a shot later she holds it in her left hand.
The agony and the 'ex'tasy - S4-E1
Continuity mistake: During credits, when the girls are walking, Carrie holds her invitation from the lower left corner in one shot but from the middle part in another.
The agony and the 'ex'tasy - S4-E1
Continuity mistake: Big's tie is tucked inside his jacket, but loose in the rest of the shots.
The agony and the 'ex'tasy - S4-E1
Continuity mistake: Inside Big's car, Carrie lowers her cup, but a shot later it's raised.
Answer: I'm a long-time fan of the show, having re-watched it many times, and I definitely remember slightly different dialogue at the end of that episode than what's on my DVD. I'm afraid I have no idea why this change might have been made or any other info, but you're not insane.
Purple_Girl