After stumbling onto a mystery at a library, the gang finds out that there are real ghosts wandering around, leading them to different areas solving small mysteries all leading up to a giant mystery concerning an ancient spell book.
The levels are very basic: there are three main objectives:
Seal all the monsters in the level.
Find the five clues.
Complete the level and its missions.
There are also collectible sandwich ingredients in each level that unlock mini-games.
The Haunting of Hambridge
Mayhem at the Movies
Weird Wild West
Bad Juju in the Bayou
Fake Ghost: He tries to attack you by running into you, knocking you back a little, causing no damage, and can turn bookshelves, also causing no damage. To beat him, suck up all of the ghosts that are following his orders. After doing this, a ghost will realize that the fake ghost isn't real, and scare him off.
Red Knight: He chases you throughout the studio. If he touches you, you instantly loose all of your cool. To beat him, run through the studio while he keeps taking damage from the traps. After two laps, run into the castle, and the Red Knight gets captured by a giant net.
Giant Dust Devil: He breaks himself into smaller dust devils while launching horses from the rapidly spinning horse ride. When you suck up enough of his dust devil pawns, The last remains of him come down in one piece. In this state, he behaves like a normal dust devil, except he is bigger, faster, and takes a longer time to suck up. Once you suck him up, you win.
Big Zombie: At first, you have to suck up the three zombies that are terrorizing the van. After you do this, The big zombie will come down and fight you. He attacks like a regular zombie, except he can stomp on the ground and send a shock wave through it, and, like a normal zombie, can breathe on you with smelly breath. To defeat him, just keep trying to suck him up until he is finally gone.
Giant Fire Ghost: This is the final boss of the game. He can launch fireballs at you, and if you activate a sprinkler, he will throw a large amount of fireballs, all at one time. If there are less than two normal fire ghosts on the field, the next fire ball he throws will summon one. Your goal is to make the giant fire ghost wither away the rocks that are blocking the sprinkler, and then activate them. Once you have activated all four sprinklers, Velma will activate the rain to get rid of the giant fire ghost's fire, but the battle is not over yet. Like normal fire ghosts, the giant fire ghost turns into a normal ghost from water. In this state, he acts like a much bigger version of a regular ghost, except he follows you. All you have to do is suck him up completely, and you will have beaten the game.
When something scares Scooby and Shaggy, their Cool Meter is drained. If the Cool Meter is totally drained, the next time an enemy catches Scooby or Shaggy, they will run away and have to start at their last save point. To replenish the Cool Meter, Scooby and Shaggy find Scooby Snacks.
Jeff Bennett - Alan Dinsdale, Walter Peabody, Robert Zabrinski, Travis Sherman, Mercanary
Tom Kenny - Earl Milton, Johnny Channayapatra, Billy Bob, Mercanary, ShermanTech Scientist
James Arnold Taylor - Jeremy Rhodes, Zombie, ShermanTech Scientist, Watchman, Security Guard
Jennifer Hale - Poltergeist, Computer Voice, ShermanTech Scientist
Mystery Mayhem was met with very mixed reviews. GameRankings and Metacritic gave it a score of 53.20% and 53 out of 100 for the Game Boy Advance version and 55.75% and 54 out of 100 for the GameCube version.