The story of Katamari Forever follows Prince Palsberg as he tries to save the universe from an evil robot version of his father, the King of All Cosmos. The King has lost his memory after knocking his head and a new robotic version is constructed by the cousins and prince must roll up junk to become a star.
The gameplay involves rolling the Katamari ball over objects in the environment, which can only roll up things that are smaller than itself. The goal is to make it as big as possible to become a star. The revisited levels take place inside the king's head and feature colouring of dreams by rolling all over them.
Katamari Forever features 30 levels, including both new and old ones from previous games. The game runs at 1080p resolution and has a cel-shaded style. It also includes local multiplayer with online leaderboards.