In an interview on the podcast Nerdist, Sarah Jessica Parker revealed that she always suspected that the three non-Carrie Bradshaw Sex and the City ladies were just figures of Carrie's imagination.

She suggested Miranda, Charlotte, and Samantha might have been "just for [Carrie's] column." In the show, for those who haven't binged on HBO Go, Carrie was a sex and relationships columnist, and her friends regularly factored into her stories. "[The friends are] such perfectly archetypal characters... [Carrie] is among them because that's her way of infiltrating story and affecting story too. To have her own actions affect those friendships [so she can] document their response," she continued.

This might sound a bit dense, so to summarize: Parker thinks Carrie fabricated her columns using a fictional group of characters whose archetypes represented women in the real world. She included herself in these otherwise fictional stories to ground them, and steer them, perhaps as some sort of moral center.

i wonder what SJP thinks about 'mr. robot'

Her theory is actually one that comes up a lot with popular TV series (ever since it turned out that Newhart was just a dream had by a character on The Bob Newhart Show) — all the babies in Rugrats are dead except for Angelica; Breaking Bad's "Felina" was just Walter White's New Hampshire death dream; every TV show ever made is just a dream that St. Elsewhere's Tommy Westphall is having, and so on. It's a question posed about The Sopranos, answered in Lost, and only winked at in Deep Space Nine. And of course, Sam Esmail will probably never get tired of teasing audiences about what's real on Mr. Robot — whether you think that's genius or lazy writing is none of my business.

Maybe the reason this feels possible so often is because the main character of a show is often the delivery mechanism for a creator's message, and the secondary characters serve the protagonist and their arc. By default, the main character will feel the most real and their actions will have the most nuanced consequences. Joss Whedon once teased Buffy the Vampire Slayer fans who thought the whole show might have been Buffy's hallucination saying "If the viewer wants, the entire series takes place in the mind of a lunatic locked up somewhere in Los Angeles... and that crazy person is me."

I'm not fully on board with her theory because this type of last-minute or after-the-fact reveal is often based on nothing but the fact that the script accidentally left room for it.

Parker's theory stemmed from the fact that she viewed her co-stars characters as mere "archetypes," but archetypes can be as fun to watch as super-nuanced characters — it doesn't make the fiction worse. The writers of SATC mined these archetypes to write hundreds of intriguing scenarios for the women. By way of sticking with Miranda, Charlotte, and Samantha for 94 episodes, the Sex and the City audience was saying their characters were real enough to feel empathy for and dramatic enough to enjoy watching. It would be almost insulting to be told that the women we fell for were just paper dolls being moved around on Carrie Bradshaw's story boards.

The only worse betrayal than yanking that away is expecting me to believe that Dan Humphrey was Gossip Girl and he spent years slut-shaming his own sister and girlfriend.