The hit series follows a team of super-powered brothers and is based on Gerard Way’s The Umbrella Academy comic series, which may provide insight into the Sparrow Academy and more importantly, the meaning of the cube.
Although its purpose is yet to be revealed, the cube is strongly connected to the Sparrow Academy. According to popular theories, there is a belief that the cube contains one of the 43 children chosen from The Umbrella Academy.
Whether it is a soul or some kind of manifestation, the fact that he was next to other team members hints that the cube is another child. The Umbrella Academy creator Steve Blackman revealed that the cube’s name is Christopher.
While some have claimed that the green cube could be Harlan Cooper based on the fact that he is levitating or even someone with time travel powers, it appears that the cube will be connected to a new character at The Umbrella Academy.
Linked theories also suggest that the cube could be an AI, assuming the role of caretaker for Grace or Pogo. Both figures were imperative in raising the Hargreeve brothers at The Umbrella Academy.
Hopefully, the live-action series The Umbrella Academy in its season 3 can provide a greater explanation for the green cube compared to the mystery that persists in the comics.