Noah Schnapp revisits Castle Byers in a Stranger Things season 5 behind-the-scenes video. Introduced in season 1, Castle Byers was a fort that Will (Schnapp) and his brother, Jonathan (Charlie Heaton), had made. When Will was trapped in the Upside Down, he hid from the Demogorgon in the alternate dimension’s version of Castle Byers. Will has gone through a great deal since then, with his story poised to conclude in Stranger Things season 5, which is still filming.