Priestley, 49, who played Brandon Walsh, left the show in its penultimate season and has since been involved in shows such as comedy Call Me Fitz (2010 to 2013).
A race car fanatic, Priestley fractured his spine in a crash on the tracks in 2002. He recovered, but quit racing after the accident.
The Canadian-American still acts regularly and has been in Canadian comedy-drama Private Eyes since 2016 as a hockey player-turned-private investigator. He will appear in a new 90210 six-part series starring the original cast, slated to air later this year.
Perhaps the cast member with the most notoriety, Doherty played Brandon's sister - Brenda Walsh.
The 47-year-old was written out of the show in Season 4 following rumours of bad behaviour, including fights with co-star Jennie Garth, which were later confirmed by Garth and producers who worked on the show.
Doherty was part of the main cast on Charmed (1998 to 2006), but left the show in Season 3, reportedly as a result of a feud with co-star Alyssa Milano.
The Beverley Hills star reprised her role as Brenda in the 2008 reboot of 90210 and was last seen in last year's reboot of classic teenage movie Heathers.
She was in the original 1988 film starring Winona Ryder and Christian Slater.
Doherty was diagnosed with breast cancer in 2015 and underwent a single mastectomy the following year. Her cancer is in remission.
Garth, 46, played Kelly Taylor on the show and was one of the few cast members who stayed through the series' 10 seasons.
She appeared on its spin-off, Melrose Place, and later the 2008 reboot of 90210. Garth, who has signed on for the new 90210 series, was one of the leads of sitcom What I Like About You (2002 to 2006).
Ziering, 54, who played the spoilt Steve Sanders, was a series regular through the 10 seasons of the show, like Garth.
While he is best known for his role in the teenage soap, he also played Fin Shepard in Sharknado (2013), a television movie about a waterspout that lifts sharks out of the ocean and deposits them in Los Angeles.
The ridiculous premise garnered the film a cult following and it went on to release five sequels, all starring Ziering as an ex-surfer who owns a bar.
Spelling, 45, played Donna Martin, whom she auditioned for under another last name as her father, Aaron Spelling, was producer of the show.
After 90210 ended in 2000, she became a New York Times best-selling author with her 2009 autobiography, Stori Telling, and went onto publish five more books.
She also acted in a string of television movies, including co-star Ziering's Sharknado franchise - appearing in last year's final film.
She was most recently on The Masked Singer, in which she was revealed to be the Unicorn in a January episode this year.
BRIAN AUSTIN GREEN
Green, 45, played Spelling's on-screen love interest, David Silver, in the series. Since the show wrapped, Green has been involved in projects including the sitcom, Anger Management (2012 to 2014).
Green is, however, better known for his real-life romances. He shares a 16-year-old son, Kassius, with 90210 co-star Vanessa Marcil, who played Gina.
But he has been married to Transformers (2007) bombshell Megan Fox, 32, since 2010.
The couple, who have three sons together, have had an on-and-off relationship. Their engagement was broken once before they married. In 2015, they separated, but reconciled the following year.
Last year, Marcil uploaded an Instagram post that accused Fox and Green of cutting Kassius out of their lives.
She said her son has yet to meet his youngest stepbrother, does not know where his father and Fox live and has been left "truly heartbroken".