Matthew McConnaghey was apparently an eleventh hour replacement for another film star, as Sarah Michelle Gellar mouths a different actor's name through her hands during her scene with Sarah Jessica Parker, with McConnaughey's name looped over on the audio.
Miranda's acquaintance at the bar says his name is Jason Dique and that it is Dutch. French words end in -que, Dutch words/last names generally do not. If it was "Dijk" it would be Dutch.
When Carrie is in the bar talking to Debbie (Sarah Michelle Gellar) about who is interested in the project, Carrie guesses "that Jennifer Love Something girl". Sarah Michelle Gellar and Jennifer Love Hewitt both starred in I Know What You Did Last Summer (1997).
The actor who Sarah Michelle Gellar mouths when talking to Carrie is Warren Beatty. And it would make more sense for the older Beatty to play Mr. Big is a movie about Carrie's column.
Sarah Jessica Parker and Matthew McConaughey later starred together in Failure to Launch.