'Bridgerton' author Julia Quinn had no idea Lady Whistledown's identity would be revealed on season 1 until she watched the finale

• Julia Quinn didn't know about Lady Whistledown's season-one reveal before watching "Bridgerton."
• In the last script she read, there was a red-herring ending. No one told her the writers changed it.

Warning: This article contains spoilers for season one of Netflix's "Bridgerton."

Despite being the architect of the Regency-era "Bridgerton" universe, Julia Quinn was completely thrown by Lady Whistledown's season-one reveal as Penelope Featherington.

Ahead of the Shondaland adaptation's December debut, Netflix sent all eight episodes to the 51-year-old author, who relinquished creative control but remained in the periphery of production as a consultant. She plowed through the series in her Seattle home, joined by her husband and their teenage son.

When the trio reached the closing moments of episode eight, specifically the scene in which wallflower Penelope (Nicola Coughlan) removes her hooded cloak and outs herself as the anonymous gossip columnist, Quinn's jaw dropped.

"We get to the last minute I was like, 'What?!'" she told Insider during a recent Zoom conversation.

"I immediately got on email and was emailing Shondaland being like, 'What just happened?!'"

'Bridgerton' writers switched the script

In Quinn's eight-part series, the author doesn't divulge Penelope's secret until book four, "Romancing Mister Bridgerton," a 2002 novel centered around Colin Bridgerton and Penelope's love story.

And though "Bridgerton" isn't a word-for-word adaptation, the writers were initially going to follow Quinn's lead by keeping the writer's identity under wraps - at least through the first season.

The last version of the script Quinn read featured an alternate ending, one that hinted at Cressida Cowper (Jessica Madsen) as Whistledown.

Coughlan confirmed during Netflix's September TUDUM panel that the cast and crew went as far as filming the scene during reshoots, even though the plan was never for the snooty debutante to actually be Whistledown. It was a distraction tactic.

Upon further consideration of how to handle Whistledown's reveal, the writers reasoned that "anybody can just Google" her true identity, thanks to the books, Quinn explained.

So, they switched the script and gave up Penelope's secret out of the gate.

"No one told me they changed the ending. So it was just kind of funny. It's the ultimate twist ending, like shocking me. I mean, you would think I couldn't be shocked."

The actors didn't know who Whistledown was either

While filming season one of "Bridgerton," the cast remained in the dark about Whistledown's identity as well. The writers intentionally threw the actors off course by handing them scripts with incorrect endings.

"We never got the right endings in the scripts, so none of the cast really knew," Golda Rosheuvel, who plays Queen Charlotte, said on an episode of "The Netflix Afterparty."

Unless the cast members read "Romancing Mister Bridgerton," the person behind the pages remained a mystery.

Even after Coughlan shot the final reveal scene for episode eight, she wasn't fully convinced she was Whistledown.

"When I got the episodes and was watching, I was like, 'Is it actually gonna be me?'" she recalled. "And then the hood came down and I was like, 'Phew. Okay. It is.'"

Aside from Quinn's role as a consultant on the forthcoming second season of "Bridgerton," which recently wrapped production but does not yet have a confirmed premiere date, she's been revisiting her early novels while writing "The Wit and Wisdom of Bridgerton: Lady Whistledown's Official Guide."

The book, published by HarperCollins on Tuesday, features a collection of each main character's most memorable lines, along with brand new society pages penned by Whistledown.