The 'Grey's Anatomy' Season 16 Guest Star Lineup Includes A 'Charmed' Reunion

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15 seasons. 342 episodes. Literally countless patients delivering heart-rending monologues about life, love, and loss at Grey Sloan Memorial Hospital. If the long-running ABC series is famous for anything (besides unlikely disasters), it's the show's revolving door of high-profile guest stars; and by the looks of the Grey's Anatomy Season 16 guest stars who will be showing up in the near future, that tradition will continue into the medical procedural's record-breaking sixteenth year.

Over the years, Grey Sloan Memorial (or Seattle Grace or whatever the hospital is called at any given moment) has played host to patients, doctors, and concerned family members played by the likes of Mandy Moore, Demi Lovato, Bernadette Peters, Sarah Paulson, Faye Dunaway, Geena Davis, Elisabeth Moss, Millie Bobby Brown, and many, many more recognizable faces. So who can viewers expect to show up in Season 16?

Earlier this month, ABC confirmed that Grey's would be staging an exciting reunion in its third episode of the season, appropriately titled "Reunited," to be aired on Oct. 10. The press release for the episode states that, "a patient at the hospital is brain-dead after falling into a construction site, and her two sisters must decide whether or not to keep her alive." Who did the network get to play those two sisters? None other than the stars of the classic WB series Charmed, Alyssa Milano and Holly Marie Combs.

Not only will "Reunited" be a reunion for Milano and Combs, but it will also be a reunion for the two Charmed stars and Grey's showrunner Krista Vernoff and writer Andy Reaser (who penned the episode in question), both of whom used to write for the WB series before their time on the ABC medical soap.

Milano's and Comb's appearance on Grey's is part of a coordinated effort across ABC to stage exciting reunion events this fall, referred to as #CastFromThePast. In addition to this Charmed throwback, audiences will also be treated to a Blues Brothers reunion on The Conners, a Cheers reunion on The Goldbergs, a Crazy Rich Asians reunion on Fresh Off The Boat, a Castle reunion on The Rookie, and many more.

While ABC is keeping any further high-profile Grey's guest stars under wraps for now, Vernoff has hinted at the possibility of the surprise return of a familiar face at some point during Season 16. "I'm trying to get someone back," the showrunner said during the show's summer press tour, as reported by TVLine — although she refused to provide any clues to help solve this tantalizing tease. "There's someone I'm hoping will make an appearance this year, [but] it's a real maybe. I'm trying."

Could the guest star in question be Sandra Oh's Cristina Yang, coming back to help her "person" after Meredith was fired? Katherine Heigl's Izzie Stevens, last seen in Season 6 after being fired and dumping Alex? Kate Walsh's Addison Montgomery, now that her spinoff, Private Practice, is a thing of the past? (One name we can probably cross off the list of candidates is Burke, given Isaiah Washington's recent headlines.)

While future guests remain shrouded in mystery, there are at least three names we know won't be returning as guest stars: Greg Germann, Chris Carmack, and Jake Borelli. No, not because their characters — Tom Koracick, Atticus Lincoln, and Levi Schmitt — are gone… but rather because the actors have been promoted from recurring guest stars to full-fledged series regulars.

With even more Tom, Link, and Glasses to come, with Charmed reunions lined up, and with blasts from the past possibly coming to haunt the halls of Grey Sloan, Grey's Anatomy certainly isn't losing steam heading into Season 16. In fact, it's shaping up to be just as exciting and action-packed as it was a decade ago.