Stranger Things star Millie Bobbie Brown treated fans to the sweetest tribute in any dimension (even the Upside Down) in honor of costar Noah Schnapp - and looked fabulous doing it. "Happy birthday to my bestest friend. Me and you against the world," the actress, 21, captioned a photo in which she embraced her costar, who celebrated turning 21 on Friday, October 3. Brown matched the wholesome vibes with an outfit that balanced comfort and style.