Just like Maxine in Stranger Things 2, Facebook didn't want to be left out of the cool kids group, which, in this case, is the mobile AR space.
The Netflix original show has added a somewhat-spoilerish camera effect to the Facebook app for iPhone and Android that places a creature from the show on your head. It doesn't give the whole show away, but it does spoil a small surprise.
The effect follows the photo filter that Netflix sponsored with Snapchat concurrent with the show's second season premiere last week.
Frankly, I'd like one that gives me hair like Eleven got this season.