Mike Wheeler (Finn Wolfhard) has also undergone a bit of a transformation in season four. In the premiere episode "Chapter One: The Hellfire Club," we learn Dustin and Mike are the proud new members of a D&D club called the Hellfire Club.
"[Mike]'s very influenced by Eddie, who's obviously a very cool guy, and he's a good bit older," Hindsgaul says. "They're all looking up to him a bit, and so, he started growing his hair out." But it's not so easy for Mike to shed that nerdy middle-school persona so fast. "He's in that awkward middle phase of experimenting, but not really getting all the way there."
Dustin (Gaten Matarazzo), on the other hand, hasn't changed much — except for one small element of his signature look. "We're actually styling Dustin's hair quite differently," she says. You just can't see it because he never takes his "thinking cap" off.