2x21 - Scooby-Doo! Mystery Incorporated

As the gang investigates a haunted house, a man resembling Fred pulls Fred through a mirror and takes him to a world where the Planispheric Disk destroyed all of Crystal Cove. Meanwhile, in the real world, Fred begins acting strangely. The real Fred manages to tell the gang that the Fred in their world is fake, having discovered so when a fake Daphne in the "mirror world" gave herself away. When the ruse is discovered, Professor Pericles uses the Kriegstaffelbots to threaten Daphne in order for the Planispheric Disk to be surrendered to him. When Professor Pericles gets the Planispheric Disk, he makes plans to free his "master.