"Stranger Things" Season 4 has yet to resume filming but a new casting report fuels a long-running theory that the team will go on a rescue mission to Russia.

The upcoming installment is looking for background actors, 18-years old and older, to play various roles. The casting call from Backstage revealed that filming for these actors will take place in Atlanta, Georgia for eight hours on still unspecified dates. They will reportedly play gymnasts, Russian types, and more.

Interestingly, the mention of "Russian" invited a lot of interest. Whether these are Russian soldiers or civilians is unclear. But it somehow fuels fans' theory that "Stranger Things" Season 4 will involve a rescue mission for Chief Jim Hopper.

Even before Netflix released the teaser trailer for the upcoming season, fans already had their theories about Chief Hopper's whereabouts at the end of the Season 3 finale. They refused to believe that he died from the blast at Starcourt Mall. Instead, they have this theory that he is alive but taken by the Russians. The trailer proved them right when it showed Hopper toiling away as a Russian prisoner.

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From Russia with love...

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How he ended up in Russia and as a prisoner is something that "Stranger Things" Season 4 will definitely reveal. How he gets out, on the other hand, according to fans will require the kids' help. The theory is that the gang will once again team up after parting ways in the Season 3 finale to plan Hopper's rescue. Eleven, Mike, Will, Dustin, Lucas, and Max will somehow find a way to get to Russia. Fans believe they will use a portal to get there quickly.

Even showrunners Matt and Ross Duffer hinted at this possibility in previous interviews. They talked about the involvement of portals that lead to "plotlines into areas outside of Hawkins." These portals will help the season "open up a little bit."

Fans will obviously see more of the Russians featured in the trailer in "Stranger Things" Season 4. The showrunners said the involvement of the Russians and their imprisoned Demogorgon (teased at the Season 3 end-credits scene) will play a huge role in the story.

Stranger Things
Noah Schnapp, Gaten Matarazzo, Millie Bobby Brown, Sadie Sink, Caleb McLaughlin, and Finn Wolfhard attend the premiere of Netflix's 'Stranger Things' Season 2 Getty