Supernatural will soon hit the decade mark, and the long-running series will bring back an old familiar face to help them celebrate.

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The CW drama wants to keep the special appearance under wraps, but executive producer Jeremy Carver recently dropped a few hints regarding the mystery guest's identity.

"We'll see one other character that we introduced a couple seasons ago who I don't want to spoil just yet," Carver told TV Line.

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This tease came directly after the EP carefully tiptoed around the possibility of a few recurring characters popping up in the 200th episode. Considering the milestone episode will bring the Chuck Shurley/Carver Edlund's Winchester Gospel to the stage, it seems pretty likely that the story of few fan favorites will feature - although probably not played by their original actors.

"Just about every character - I'll say they will be represented - that you've ever loved or hated on the show, and I say that very obliquely on purpose," Carver told TV Line. "So they will be there in spirit."

Since Gabriel (Richard Speight Jr.) and The Ghostfacers (AJ Buckley and Travis Wester) returned during season 9, Sheriff Mills (Kim Rhodes) is already confirmed for season 10, and execs already ruled out the return of Adam Milligan (Jake Abel), who do you think the mystery guest will be? Tell us in the poll below!

Find out more when Supernatural returns to The CW on Oct. 7 at 9 p.m. ET. Click the video below to see the final moments of season 9.