'Supernatural': Mark Sheppard Possibly Returning

Mark Sheppard has fans speculating that he could be coming back to Supernatural this season with [...]

Mark Sheppard has fans speculating that he could be coming back to Supernatural this season with his latest Instagram post.

Sheppard put a selfie up online on Sunday, showing his home laid out behind him and a sly smile on his face. The actor wrote a long and somewhat cryptic note in the caption, revealing that he is "reuniting with some old friends!" judging by how he left things off with the Winchester brothers, some fans are hoping that his new secret project is Supernatural.

(Photo: Instagram / Mark Sheppard)

"Getting ready to start a brand new adventure tomorrow!" Sheppard wrote. "Still super-secret, but looking forward to reuniting with some old friends! A brand new character to play, hope you will embrace him like you have the others."

Sheppard included the hashtag "SPN Family," which tends to relate to Supernatural. His post exploded, with well over 100,000 likes and a litany of comments speculating what he was working on. The fact that he is playing "a brand new character" suggested to some that he could not possibly be back on The CW's beloved series, while others took the hashtag as certain proof.

"Can't wait to see where you pop up again! It's always an adventure. Thank you!" one person wrote.

"I'm feeling like this is a riddle that he wants us to figure out," wrote another. "So look at the capitalized words. He's HAPPY to be WORKING on a NEW project with OLD FRIENDS but it's filmed in Atlanta. Anyone have another idea other than Supernatural bc it's obviously not supernatural but it is ppl he's worked with before."

"As much as I would love to see you back on SPN There is one show known for being filmed in ATL," added another. "Hanging out with walkers and a Winchester?"

Beyond Supernatural, the top guess for Sheppard's new role was The Walking Dead. The series features Jeffrey Dean Morgan, who was once on Supernatural, explaining the "old friends" element of his post. In addition, the show will need some fresh characters coming in, as series hero Rick Grimes (Andrew Lincoln) is on his way out.

Sheppard played Crowley, King of the Crossroads for years on Supernatural. He left the show in season 12, sacrificing his life to seal Lucifer in another reality. Of course, on Supernatural any character could be brought back with reasonable explanation. As it stands, Crowley is the second longest-running villain on the show after Lucifer himself.