There's a lot that "Stranger Things" fans don't know about Hopper's life before he became Eleven's papa, and Harbour told Entertainment Tonight that we're going to learn all about it. "There's some fun stuff that we're doing this season, but it's also the heaviest dramatic stuff I've ever had to do," Harbour said. "We get to see a lot of Hopper at his most vulnerable, we're gonna reveal a lot of backstory points that we've only hinted at in boxes in his attic. We're gonna see a lot of these different threads, and also, we get to see a rebirth of him." Those boxes, you may recall from Season 2, are labeled "Dad," "Vietnam," and "New York."
He elaborated a bit more later in the interview: "There's one thing in it that plays very big in this season that I've known since the first frame of the first season. Me and the Duffers would sit around and speculate, 'Oh, wouldn't this be cool?' the minute we started shooting," Harbour said. "We never thought we'd even get a second season, and then we get to do it in this season. It's so satisfying to have had an idea five years prior, and to go like, 'Oh, this is a season when we're gonna let out this secret that we were using just as a subtle thing to inform something.' We're gonna lay it out finally, and it's really cool."
It's a vague enough tease that we have no idea what he might be talking about. For instance, what if he is Will Byers' (Noah Schnapp) biological father?
We're just throwing out an idea, not saying it's a good one! We'll find out for sure what Hopper's secret is whenever Netflix finally releases "Stranger Things 4."
