- The Gossip Girl book series was originally going to be adapted into a movie starring Lindsay Lohan, but it never materialized, which is when Stephanie Savage and Josh Schwartz took over the project and developed it for television. Schwartz, who had just come off of The OC, was skeptical about making another teen drama, but he was attracted to telling the stories of Upper East Side teens, who he deemed were "worldlier" than those in Orange County.
- Blake Lively and Penn Badgley were home schooled together as children. Their on-screen romance as Serena and Dan led to a real-life relationship, which ended while their characters were still involved.
- Leighton Meester, a natural blonde, was not allowed to audition for Blair until she dyed her hair brown.
- Ed Westwick originally read for the role of Nate Archibald, but was flawlessly cast as Chuck Bass instead. Chace Crawford was then cast as Nate. The CW was against hiring Ed at all, insisting that he looked more like a serial killer than a romantic lead.
- Kristen Bell didn't audition to voice Gossip Girl. Instead, she simply called the producers and told them she wanted the part. And nobody says no to Veronica Mars.
- Penn openly admits to having originally turned down the role of Dan Humphrey before eventually accepting it. He also didn't like to memorize his lines, which must have made him a joy to work with.
- Despite being one of the CW's most successful shows ever, Gossip Girl initially pulled in disappointing numbers. However, it was the first show to point out the changing landscape of television, as it almost doubled its ratings with DVR viewings and it routinely topped the iTunes episode charts.
- The show filmed in Paris on several occasions. The CW initially warned against this, as the show wasn't popular in Europe and was in danger of being taken off the airwaves.
- Blake and Leighton had a notoriously bad relationship, taking their on screen frenemyship to the real world! Not surprisingly, the reports stem from the series' very obvious shift in focus from Blake's Serena to Leighton's Blair.
- The Parent Television Council, which specializes in ruining everyone's fun, often targeted Gossip Girl, especially during its first season. So what did the show do in response? It took quotes from the PTC's criticisms, like "Mind-blowingly inappropriate" and "Every parent's nightmare," and used them in the second season's promotional campaign.
- It was heavily reported that Taylor Momsen would be given her own spin-off, as her character Jenny Humphrey fronted The It Girl novel series. But really, the exact opposite happened. The CW didn't pick up the spin-off, and Taylor only appeared in a handful of episodes during the show's fourth season before leaving altogether to focus on her music career.
- The second season, "Valley Girls", which focused on Lily van der Woodsen's teenage exploits in 1980s California, was a backdoor pilot for a potential spin-off that was never picked up. The episode starred Brittany Snow as the teenaged version of the character, and the spin-off would have featured younger characters of characters from The OC, officially linking Schwartz's two shows.
- Cecily von Ziegesar, the author of the novelist, criticized Vanessa as "the one character the show ruined." While the novel depicts her as bald and wearing all black, the show portrayed her as an annoying, self-righteous hipster.
- Connor Paolo, who played Eric van der Woodsen, repeatedly rejected producers' offers to become a series regular for personal reasons. He appeared as a recurring guest star for the first four seasons before leaving the show to star in Revenge.
- Mischa Barton was originally offered the role of Georgina, whose last name was changed to Sparks from Spark in the novels. Michelle Trachtenberg was cast in the role and would become a critics' favorite. Aside from the main cast, she is the only character to appear in all the season finales.
- January 26, 2012 is Gossip Girl Day in New York. Mayor Bloomberg visited the set and proclaimed the date as such, commending the cast and crew for glamorizing showcasing the city so well.
- Kaylee DeFer originally auditioned for Raina Thorpe before she was cast as the UES's resident cunt, Ivy Dickens.
- William Baldwin, who played William van der Woodsen, avoided meeting Blake in person until they filmed their first scene, so that they could better depict their characters' estranged father-daughter relationship.
- In the books, Eric is Serena's older womanizing brother who rarely appears. In the show, he's introduced as Serena's younger suicidal brother. Toward the end of the first season, Georgina accidentally outs him as being gay.
The writers never planned to reveal Gossip Girl's identity, which may be why the series finale's revelation of Dan as the anonymous blogger is completely implausible. (Look it up on Tumblr. Hardcore fans have a million and one reasons why it's just not possible.) In fact, when pilot test audiences suspected that Dan was Gossip Girl, the episode was re-edited, not because producers wanted to protect the secret, but because they never intended for Dan to be GG in the first place! Penn himself was not informed about his character's alter ego until the night before he filmed the scene.