Who could have known when Sarah Jessica Parker, Cynthia Nixon, Kim Cattrall and Kristen Davis filmed the “Sex and the City” pilot in 1997 that it would become not only a phenom but a 21st-century film franchise?

“None of us,” says Nixon. Back then, the stage actress was happy just to land a series that shot on home turf in New York. “For me, television seemed a non-possibility because they shot in Los Angeles or Canada, and I wasn’t willing to relocate.”

“Sex” hit so big, she believes, “because we showed single women who were unmarried who were having a great life. There hadn’t been that many depictions of that. Before, if you were 30 or 40 and unmarried, it was often a disaster.”

With the second movie due, she adds, “people have just grown very fond of the characters, the wit of the writing and the glamour and the fashion and all that.

“One of the things that has kept it so strong is that (writer-director) Michael Patrick King doesn’t try to take us through the same thing because it worked so well the last time. If we stayed the same, going out and drinking and having sex, we would turn into ‘Absolutely Fabulous,’ which is not what we are. He has allowed us to age, and the audience has allowed us to come along for the ride.”

The first “Sex and the City” film, Nixon says, “was more heavy and almost tragic. Now we’re on the road and almost carefree. One thing that’s so nice is that there is so much of all us together. We’re all off on an adventure.”