The Odyssey (1992)

When 11-year-old Jay Ziegler falls from a treefort after being pursued by bullies who wanted his father's precious telescope, he ends up in a coma - in the real world (known as the Upworld). In the Upworld, Jay's mother Val, his best friend Donna and the bully Keith all try to cope with their reality. In the Downworld (Jay's mind), Jay finds himself in a world entirely populated by children, where he meets up Alpha and Flash (the Downworld counterparts of Donna and Keith) and the trio embark on a mysterious mission involving a telescope, the land's mysterious leader Brad, and a connection to Jay's father.