The Ghost was the disguise of Shaggy Rogers.
Physical appearance[]
The ghost was a man dressed in a white astronaut uniform with the American flag on his left arm and a black visor.
Personality[]
He was evil, and was looking forward to putting an end to the production of the new Scooby Snack prototype.
History[]
Scooby-Doo! 50th Anniversary Giant[]
Shaggy Rogers unmasked.
The ghost disguise was simply used to bring Scooby to the exact spot where his birthday party was set up. After some confusion with Shaggy as the supposed "ghost" and the Scooby Snacks Factory CEO dressing as Shaggy, they explained most of the other things involved with the plan, and Scooby's birthday was celebrated shortly after.