There are moments where Stranger Things gets so lost in its own extradimensional mythos, you can forget that most of the other residents of Hawkins are living perfectly normal, everyday lives free of demogorgons. But the show makes a point of pulling you back to reality with characters such as Erica, Lucas' little sister.
Though she's only in a few shots of Stranger Things 2, antagonising her brother and his nerdy friends, Erica (Priah Ferguson) leaves the kind of lasting impression that makes you think to yourself, "Yeah, I wanna see this kid fighting Lovecraftian demons, too." According to the Duffer Brothers, Ferguson's performance as Erica made it clear that her role needed to be expanded a bit for the series' second season. In an interview with Yahoo!, the Stranger Things co-creators described how they first found Ferguson and how they're already planning on what to do with Erica going forward.
Said Ross Duffer:
There will definitely be more Erica in Season 3. That is the fun thing about the show - you discover stuff as you're filming. We were able to integrate more of her in, but not as much you want because the story [was] already going. 'We got to use more Erica' - that was one of the first things we said in the writers' room.
Ferguson herself has been vocal about her interest in coming back to Stranger Things and gone so far as to theorise just how her character might react to learning about the secret adventures Lucas and the others have been having. Speaking to Vulture, Ferguson reasoned that Erica would probably process everything about the Upside Down in stride:
It would be cool if I were back, and maybe also get into fighting the demogorgons, because my response from when I was looking through Lucas' room for He-Man, I think is a little clue that Erica may be sneaky and may find something from the demogorgon.
Stranger Things is going to have to keep switching things up if it wants to keep its core of characters interesting as the series progresses. We're already beginning to see how the first signs of puberty are testing the gang's bonds with one another and as that whole situation continues to get more awkward, it'd be fantastic to have someone around to cut through all the nonsense with a sharp sense of humour.