Ghost of a customer

The ghost who said it was a former customer of Eddy's Burgers was the disguise of a cook at Voltaire's restaurant.

Physical appearance
He had blue-gray hair and blue skin, with a large bone protruding from his throat.

Personality
He claimed to have choked on a bone and died at the restaurant, and he warned others to leave before they met with a similar fate.

Scooby-Doo (DC Comics)
The cook at Voltaire's restaurant was in the pay of a big conglomerate, who wanted the location of both Voltaire's Pizza in a Cup and Eddy's Burgers for its own business development. He ruined Voltaire by suggesting he try selling "pizza in a cup" instead of regular pizza, but Eddy wasn't so easy to influence and his food was too good, so he dressed up as the ghost to drive his customers away. Velma Dinkley knew he was a fake right away, since he claimed to have choked on a bone and burgers don't have bones. Shaggy Rogers and Scooby-Doo went undercover as workers at the burger place for all the food they could eat, and their actions lured the ghost into being captured.

Appearances

 * Scooby-Doo! (DC Comics)
 * Phast Phood Phantom