When TV shows lose their stars

Jennifer Morrison in ABC's "Once Upon a Time."

(CNN)It's time for Emma Swan's swan song on "Once Upon a Time."

Jennifer Morrison has announced she plans to depart the ABC fantasy series after its current sixth season.
"After very careful consideration, I have decided that creatively and personally, it is time for me to move on," Morrison said in a note posted to Instagram.
"Once Upon a Time" has not yet officially been ordered for a seventh season, but there have been reports that ABC was considering renewing and retooling the series, with Morrison's character and three other regulars (Lana Parrilla, Robert Carlyle and Colin O'Donoghue) at the center.
    It's unclear how Morrison's decision affects plans to revamp the show or its chances for renewal.
    Morrison said she's agreed to return for one episode in Season 7 should the show continue.
    The Season 6 finale airs May 14.
    Though "Once Upon a Time" has been billed as an ensemble piece and added a number of new characters since its 2011 debut, it was undoubtedly a story that largely centered on Emma Swan, a woman who stumbles into a world with fairy tale characters, villains and a pair of long-lost parents named Snow White and Prince Charming.
    The latter seasons backed away from the idea that Emma was a sort of audience surrogate in the strange world, but it stands true that losing the character will require a major plot adjustment.
    However, as other shows have proven, it's not impossible to continue a show without one of its stars.

    The shocking death

    There is much story to be gained from a shocking death and that's why it seems to be the fallback for desperate storytellers who suddenly lose access to an actor.
    Most recently, "Nashville" had to deal with the departure of Connie Britton, who chose to leave the show after five seasons and was the top-billed actor on the series.
    Creatively, the death of her character Rayna gave the series emotional fuel and a bump in ratings, enough for it to earn a Season 6 renewal.
    Derek Shepherd's last episode of "Grey's Anatomy."
    Patrick Dempsey's exit on "Grey's Anatomy" initially shocked fans and left some vowing never to watch the series again. But the death of Meredith Grey's (Ellen Pompeo) great love made room for stories that had nothing to do with her romantic life.
    "Grey's Anatomy" was renewed for Season 14 in February.
    Other characters who joined the Suddenly Deceased Club: Dan Steven's Matthew ("Downton Abbey"), Misha Barton's Marissa Cooper ("The O.C."), Nicole Beharie's Abbie ("Sleepy Hollow"), and Josh Charles' Will Gardner ("The Good Wife").

    The long goodbye

    When a star gives plenty of notice before exiting an iconic role, it's evident on screen.
    The news may not always be welcome to fans, but it certainly gives writers ample time to craft proper stories.
    Michael Weatherly announced his "NCIS" exit months before the end, allowing writers to put in motion a storyline about Tony DiNozzo reassessing his priorities.
    Steve Carrell's decision to leave "The Office" after Season 7 was also given with plenty of lead time. The result was an arc that had Michael leaving Scranton to pursue the life he always wanted to the love of his life and a number of emotional goodbyes between Michael and his co-workers.

    The sudden departure

    Sometimes, people just stop talking to you with little to no explanation -- even TV characters.
    Elliot Stabler (Christopher Meloni) retired without a proper goodbye to partner Det. Olivia Benson.
    Izzy Stevens (Katherine Heigl) left Seattle after breaking up with Alex on "Grey's Anatomy" and was never heard from again.
    Cindy Williams's Shirley said farewell to Laverne with a note on "Laverne & Shirley."
    Getting ghosted in real life is not fun. Getting ghosted by a TV character? That's downright insulting.

    The crazy twist

    "Once Upon a Time" has a unique set of circumstances ahead of it should it try to continue without Morrison.
    First, the series is extremely serialized, meaning it can't pull off a Dear John letter departure in a satisfying way.
    It also won't have the luxury of crafting a long and winding exit since Morrison has agreed to a one-episode return.
    So what's left? The crazy twist.
    "The Vampire Diaries" is the most recent show to pull this off convincingly.
    The show had to find a way to put Elena Gilbert on the sidelines after Nina Dobrev decided to leave the show, and they did so by leveraging the show's greatest asset -- its supernatural roots.
    Elena was put into a supernatural coma, so she was out of the day-to-day action but it left the door open to a possible return. (Dobrev did end up resurfacing for the series finale.)
    The question now is if "Once Upon a Time" will give its leading lady a storybook ending or dark demise.
    To be continued...