|Previous Season:||Season Seven|
- Regina the Bandit
- Robin Hood (Grimm Realm)
- Huntsman (Grimm Realm)
- Queen Snow
- Snow White (Grimm Realm)
- Prince Charming (Grimm Realm
- Lana Parrilla as Regina Mills/The Good Queen and Regina the Bandit
- Ginnifer Goodwin as Snow White and Snow White (Grimm Realm)
- Jennifer Morrison as Emma Swan
- Colin O'Donoghue as Killian Jones and Rogers
- Josh Dallas as David Nolan and Prince Charming (Grimm Realm) 
- Rose Reynolds as Tilly
- Tiera Skovbye as Margot
- Adelaide Kane as Ivy Belfrey
- Keegan Connor Tracy as Blue Fairy
- Rebecca Mader as Zelena
- Robert Carlyle as Rumpelstiltskin
Special Appearance By
- Andrew J. West as Henry Mills
- Dania Ramirez as Jacinda Vidrio
- Mekia Cox as Sabine
- Jeff Pierre as Drew
- Alison Fernandez as Lucy
- Meghan Ory as Ruby
- Teri Reeves as Dorothy
- Sean Maguire as Robin Hood (Grimm Realm) 
- Jamie Dornan as Huntsman (Grimm Realm) 
New Cast Members
Special Appearance By
- Mekia Cox is now billed as guest starring.
- Alison Fernandez is now billed as guest starring.
- Dania Ramirez is now billed as guest starring.
- Andrew J. West is now billed as guest starring.
- Jared S. Gilmore is now billed as special appearance by, previously billed as special guest starring.
- Josh Dallas is once more billed as starring
- Ginnifer Goodwin is once more billed as Starring
- Jennifer Morrison is once more billed as Starring
- Rebecca Mader is once more billed as Starring
- Tiera Skovbye is now billed as Starring
- Rose Reynolds is now billed as Starring
- Adelaide Kane is now billed as Starring
- Keegan Connor Tracy is now billed as Starring
- Sheriff Henry will appear more than Henry Mills, Jacinda Vidrio, Sabine, Drew and Lucy.
- Wilhelm will be the main antagonist of the season. 
- The final member of the Coven of the Eight will be revealed.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Once Upon a Time Revived for Season 8
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Three Leads Gain Second Characters, Two-Ex Leads Recurr in New Roles and One New Character Cast in OUAT
- ↑ 3.0 3.1 3.2 Once Upon a Time Season Eight Rearranges Main Cast
- ↑ Once Upon a Time’s Revival’s Final Regular Revealed
- ↑ 5.0 5.1 Robert Carlyle to Stay On
- ↑ 6.0 6.1 6.2 Jared and Alison To Recur
- ↑ 7.0 7.1 On Tiana and Naveen Returning
- ↑ 8.0 8.1 8.2 Season 8 Hot Seat
- ↑ 9.0 9.1 Once's Eighth Season Synopsis
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