Will Jamie Dornan return to ABC's Once Upon a Time for its upcoming landmark 100th episode?

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Once Upon a Time is bringing back a whole slew of characters for its 100th episode, including Peter Pan (Robbie Kay), Cora (Barbara Hershey), Cruella de Vil (Victoria Smurfit) and Sidney Glass (Giancarlo Esposito). So it stands to reason that Sheriff Graham (Dornan) would return too, right?

Wrong. Entertainment Tonight asked OUAT co-creators Edward Kitsis and Adam Horowitz if either Dornan's Sheriff Graham or Sebastian Stan's Jefferson would return for episode 100 at the outlook does not look good.

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"You know, I would not hold your breathe for either of those characters," Kitsis said. "Unfortunately, those two [actors] are very hard to pin down."

Dornan is now one of the most sought-after actors in Hollywood after starring in Fifty Shades of Grey. Meanwhile, Stan is busy with the Marvel Cinematic Universe.

As far as who will be in the 100th episode, Horowitz teased, "There are some villains and there are some non-villains in there too."

Kitsis added, "When you see where were going, you'll understand why. But I would say that for us it is the 100th episode, so we want to celebrate the show and bring back some familiar faces that we've met along the way."

There will probably be even more cameos in the 100th episode that have not been announced yet. The 100th episode will air this spring.

Once Upon a Time airs Sundays at 8/7c on ABC.