Shannen Doherty
After departing 90210 during the fourth season under a storm of controversy, Doherty, who played Brenda Walsh, appeared in film Mallrats and made a return to TV as one of the three leads of supernatural series Charmed, a role that also ended dramatically. Since then, the actress has returned to 90210 (in the first reboot, playing Brenda once again) and, most recently, in the revival of Heathers (having appeared in the original film in 1988), as well as taking part in a number of reality shows. She has also battled serious health issues - she was diagnosed with breast cancer in 2015, but is now in remission.
Jennie Garth
Like her onscreen frenemy Doherty, Garth, who played Kelly Taylor in all 10 seasons of 90210, has worked mostly in TV since, most notably in sitcoms What I Like About You and Mystery Girls alongside Tori Spelling. She has also featured in reality shows like The Jennie Garth Project, Dancing with the Stars and as a guest judge during Season 9 of RuPaul's Drag Race. Garth is also due to appear in the upcoming 90210 reboot.
Brian Austin Green
Another 10-season stayer, Green (David Silver) racked up a string of TV credits following 90210's demise, including in Freddie, Terminator: The Sarah Connor Chronicles, Desperate Housewives and, most recently, Anger Management. Green has also received a lot of press attention in recent years due to his on-off relationship with Megan Fox, and has signed on for the 90210 reboot.
Tori Spelling
Green's onscreen love interest, Donna Martin, also lasted the distance, appearing in all 10 seasons of the show. Since then, Spelling has had guest roles in a number of TV shows (as well as featuring in the aforementioned Mystery Girls) and made several telemovies (including The Last Sharknado: It's About Time in 2018), but is best known for her reality series that focus on her relationship and family life with husband Dean McDermott. She'll appear in the upcoming reboot as well.
Ian Ziering
Up until 2013, Ziering, who played Steve Sanders in all 10 seasons was best known post-90210 for his voice work in animated series like Biker Mice from Mars and Godzilla: The Series. But in recent years, he's been the star of the horror spoof Sharknado series of telemovies, playing the lead role in the original and its five sequels. Next up, he'll be seen in superhero series Swamp Thing and in the 90210 reboot.
Gabrielle Carteris
Carteris played Andrea Zuckerman for the first five seasons of 90210, leaving the show to host a daytime talk show. When Gabrielle was cancelled after one season, the actress worked mainly in telemovies and as a guest star in TV shows, including 90210, to which she returned for a few short stints. Behind the scenes, she is the president of actors' union, the Screen Actors Guild, but will return to the screen in the reboot.