Brooke mentions to Carrie that, "one day, John-John (John F. Kennedy, Jr.) is out of the picture and we're just glad to have a guy that can throw around a frisbee." Sarah Jessica Parker famously dated JFK Jr. in 1991.
When Carrie and Stanford are supposedly leaving the Lincoln Center after the ballet, the people around were not extras. The scene was shot at around 10 pm when they were all exiting the center after shows.