Board Thread:Spoilers!/@comment-26837468-20150311103729/@comment-1916997-20150315142249

Chameleon-Guy wrote:

She very well could have already been filming for the Cruella episode or some of the other episodes, we don't always know everyone who's filming for every episode. But in this season we knew pretty much every guest star who was gonna show up.

And yet roles like Granny, Grumpy, Ingrid, Bo Peep, Ruth, Blue, and The Apprentice were not annonuced or seen. So it really just depends.
 * Sidney's return was announced
 * Ella was confirmed in a tweet
 * Aurora in 4x07 was confirmed in an interview
 * Zoso was announced
 * Blackbeard was seen on set
 * Archie was seen on set on 4x03, and it's been said he will show up again because Pongo will meet Cruella
 * Robin and Marian were confirmed to return after 4x11 aired
 * August was announced to return
 * Ariel was confirmed in an interview
 * Cora was confirmed in an interview
 * Lily was confirmed in an interview
 * Zelena was announced to return in a flashback, and we saw her on set in present day
 * Pinocchio was confirmed in a tweet
 * Marco was seen on set
 * Smee was seen on set
 * Maleficent was announced before the season started (I think)
 * Cruella was spoiled in a tweet by Victoria Smurfit
 * Ursula was seen on set before being announced