Based on Alloy Entertainment's book series by Cecily Von Ziegesar, CW's Gossip Girl gave New York's fashionable Upper East Side basically the same slick and sexy treatment as Fox's The O.C. had given California's Orange County. The series focused on a group of terribly wealthy, dazzlingly good-looking young men and women, all attending a high-end prep school. At the outset of the story, the previously unquestioned social supremacy of teenaged rich-bitch Blair Waldorf (Leighton Meester) was suddenly and unexpectedly placed in jeopardy by the return of Blair's former best friend Serena Van der Woodson (Blake Lively), who'd just been booted out of boarding school. An unabashed "party animal" and romantic predator, Serena not only threatened Blair's position as the school's unofficial leader, but also tried to move in on Blair's handsome-hunk boyfriend Nate Archibald (Chace Crawford). These momentous events were observed and commented upon by Blair's current best buds Kati (Nan Zhang) and Isabel (Ed Westwick), and by the series' obligatory "blue-collar" characters, likable Dan Humphrey (Penn Badgely) and his socially ambitious sister Jenny (Taylor Momsen)--the latter unwittingly targeted for eventual seduction by the school's resident Lothario, Chuck Bass (Nicole Fiscella). The titular "Gossip Girl," played by Kristen Bell, dished out all the dirt on her online website, thus acting as the series' unofficial narrator. Originally planned as a theatrical feature starring Lindsay Lohan, Gossip Girl ended up being developed as a TV series by The O.C.'s Josh Schwartz, and in this form made its debut as a pilot on September 19, 2007, and as a weekly offering on October 1 of that year.