Don't get me wrong, this was a great movie and I like it! however, Having watched Stranger Things, I'm beginning to think they kinda copied the concept..........minus the scary clown of course lol.
shareOr.....the other way around.
shareThe movie began filming before Stranger Things was released and became huge. So there was no copying going on and they probably filmed too many key scenes to update from the 50's to 80's because of Stranger Things' success, which also means they didn't purposely cast the main kid from Stranger Things in IT just because of how popular Stranger Things was. He was already filming his scenes before Stranger Things was released and blew up in popularity. And if they cast him just because he was in the show, they probably would've cast him as Bill since he played the leader of the group of kids in Stranger Things and Bill is pretty much the leader of the group of kids in IT.
shareAdding to what's been said, "It" was likely a bigger inspiration on "Stranger Things" than vice versa. Maybe not this film specifically, but the Stephen King novel in which this film was based on (and this 2017 adaption follows it pretty closely). I mean I know where you're coming. It's easy to see why "Stranger Things" would come to many viewers' minds when watching this "It"... especially when you have Mike from ST appearing in both.
But bottom line is, "It" didn't copy "Stranger Things" in any way. If the film was inspired by anything other than its source material, I'd say it was a few of the 80's movies that the hit show took cues from. Anyway, I love both!