The Grim Adventures of Billy & Mandy on Wii is a chaotic brawler that tries to capture the humor and zany world of the cartoon. It features a cast of beloved characters and wacky weapon pickups, adding variety to the frantic multiplayer battles. However, the gameplay feels repetitive, levels are unimaginative, and the story mode lacks depth. Fans of the show might get some short-lived amusement out of the game's humor and references, but the overall experience feels shallow and unpolished.