The continuity, which progresses in real time,[5] was introduced in 1990 with the debut of Darren Star's teen drama Beverly Hills, 90210, which was produced by Aaron Spelling and initially aired on the FOX television network in the United States.

The unexpected worldwide success of this project, as well as that of the spin-off Melrose Place, was largely credited with launching Star's career, while bringing early fortune to FOX in the process.

[9] Melrose Place was initially inspired by Star's own professional aspirations during his 20s,[8] while Models Inc. was born when FOX asked Spelling for an eight-part summer series.

[18] Emmy-nominated scribe Charles Rosin joined Beverly Hills, 90210 in its first year and served as a writer and executive producer, scripting several episodes in seasons to come along with his wife Karen.

[21] Charles Pratt, Jr. and Frank South worked closely with Darren Star in writing early seasons of Melrose Place, helping to set the tone of the series as it grew in popularity.

[26][27] Also made famous via the first program was male lead Jason Priestley, who earned Golden Globe nominations and began a directorial career via the series,[28] and actor Luke Perry, who won acclaim and drew comparisons to James Dean.

[33] In addition, several actors known for their work in American daytime television—including Kristian Alfonso,[34] Stephen Nichols,[35] Jack Wagner,[36] and Vanessa Marcil[37]—have made appearances in the franchise.

[46] Dean Cain, who would go on to star in Lois & Clark: The New Adventures of Superman, appeared in Beverly Hills, 90210 during 1992,[47] while Eddie Cibrian, later known for his role in Third Watch, guest-starred in 1996.

[50] Debuting on October 4, 1990, the first series initially followed the teenage lives of several friends who attended the West Beverly Hills High School: Brandon Walsh (Jason Priestley), Brenda Walsh (Shannen Doherty), Kelly Taylor (Jennie Garth), Steve Sanders (Ian Ziering), Andrea Zuckerman (Gabrielle Carteris), Dylan McKay (Luke Perry), David Silver (Brian Austin Green), Scott Scanlon (Douglas Emerson), and Donna Martin (Tori Spelling).

[51] Originally, the series centered around the culture shock of twins Brandon and Brenda as they adjusted to the new experiences and friends that awaited them upon their family's move to Beverly Hills.

[52] As the show progressed, however, it gradually became more of an ensemble cast drama, with equal attention given to the familial issues, academic matters, career aspirations, and love lives of the other characters.

[63] With the progression of the second season—which was highlighted by divorce, blackmail, revenge, character revamps, and much angst between couples—the show had begun to secure a reputation for darker, more extraordinary story lines.

At the beginning of the first episode, actors Grant Show and Daphne Zuniga briefly appeared as their Melrose Place characters, seeing off a young model named Sarah Owens (Cassidy Rae) as she headed to the agency.

Instead, the writers chose to explore the ensemble cast from the start and immediately present the kind of story lines that had made Melrose Place famous.

[69][70] Primary antagonists included several figures from the models' pasts—including a stalker, a jealous sister, and Grayson (Emma Samms), the cunning and powerful ex-wife of Monique's fiance.

Jake Hanson, who was originally introduced in the continuity's first show, was the only character to appear in both Beverly Hills, 90210 and Models Inc.[66] Premiering on September 2, 2008, 90210 was produced by CBS Television Studios.

Like Brandon and Brenda 18 years before, Dixon and Annie meet several new friends who comprise the rest of the cast, including Erin Silver (Jessica Stroup), the half-sister of David and Kelly from the original series.

[3] In addition, Joe E. Tata made guest appearances, reprising his role of Nat Bussichio, owner of the Peach Pit coffee house where Dixon worked.

On January 19, 2009, Entertainment Weekly confirmed that Todd Slavkin and Darren Swimmer were installed as showrunners of a Melrose Place spin-off, which used the same title as the previous show.

[18] Ashlee Simpson, Shaun Sipos, Jessica Lucas, Stephanie Jacobsen, Katie Cassidy, Michael Rady, and Colin Egglesfield were cast in regular roles.

Throughout 2009, it was also revealed that Laura Leighton, Thomas Calabro, Josie Bissett, Daphne Zuniga, and Heather Locklear would make appearances as their characters from the original series.

[79] The bulk of the original cast is attached, including Garth, Spelling, Shannen Doherty, Jason Priestley, Ian Ziering, Brian Austin Green and Gabrielle Carteris.

Titled BH90210, the series was set outside of continuity and featured the cast playing "heightened versions of themselves" in an irreverent drama "inspired by their real lives and relationships with each other.

[108] Entertainment Weekly's Ken Tucker criticized the original tone of Melrose Place in a 1992 article, stating that "on this show, everybody's a philosopher—even more unusual, a philosopher with a cute bottom."

Despite giving the series a mixed review, he admitted to being "hypnotized by it" and added that "Melrose is the guilty pleasure that adds some salt and sweat to summertime TV.

"[109] The show received an overhaul as it advanced toward its second season, with TV Guide citing the "bed-hopping, backstabbing and cliffhangers" as key factors in its success, also noting the arrival of Heather Locklear's Amanda Woodward.