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'Stranger Things 4' Uncanny Valley: Who Plays The Younger Eleven?

If young Eleven looks slightly different to you, there's an explanation for that.

Millie Bobby Brown has a body double in flashback scenes. 

Finished binging the final episodes of season 4 of Stranger Things? They featured the younger version of Eleven (Millie Bobby Brown), but she might have looked a little different for some. It can probably be explained by a body double and deepfake technology being used to recreate scenes in the past.

"We used an amazing actress who played my body," Bobby Brown explained in an interview with MTV, published in June. Eleven's stand-in is played by Martie Blair. "I went to LA and I worked in this amazing thing called the egg, the 'Lola egg,' Bobby Brown continued. "And we basically worked in there for three days, and we did facial expressions. We did every single scene from start to finish, just using my face. No action. So it was just me turning my face, doing the whole scene as her. And then they deepfaked it onto her little body, Martie's body."

Brown added, "Incredible, incredible work. I did nothing. I can't imagine what they were doing for two years. I did three days of that and it was exhausting enough."

The latest season sees Eleven return, via flashback, to her old stomping ground in Hawkins Lab. However, this time she explores lost memories of what happened there, including her interactions with a certain lab orderly named "Peter Ballard" (we later find out this name is a massive misdirection). In order to film these scenes, a stand-in was required for Millie Bobby Brown, given the age difference.

The unfortunate byproduct of using facial mapping technology is that Eleven occasionally gives off uncanny valley vibes. Not to mention the occasional confusion over old Eleven and young Eleven's interactions with the flashback -- sometimes they're both included in the scene. On top of that, sometimes old footage of Bobby Brown's original Eleven scenes appears to be used, further emphasizing the uncanny valley moments when they come.

Regardless, that doesn't take away from Blair's performance. The young actor shared behind-the-scenes pictures of her time working on the show, including her counterpart providing extra direction.

And here's Blair with Jamie Campbell Bower, another new addition to season 4's cast.

"Thank you @Milliestopshate for being such an inspiration to me, when I showed up on set, you came right up to me. You made me feel so comfortable and welcomed. Thanks for spending time with me and helping me make my scenes AWESOME!!!," Blair tweeted, with a photo of her and Bobby Brown in front of a smashed mirror inside Hawkins Lab.

The Stranger Things writers' account tweeted a behind-the-scenes look at Bobby Brown providing Blair with direction.

Stranger Things vol. 2, aka the final two episodes of season 4, arrived July 1 on Netflix.