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The Ghost Gown is one of Professor Elvin Gadd's many inventions, appearing in Mario & Luigi: Superstar Saga. It appears as a pale blue gown with a white collar at the neck. As its name suggests, the wearer transforms into a partially-visible "ghost."
E. Gadd introduces the invention in Starbeans Cafe, drawn by the scent of a new drink. Using the gown, he is able to become a "ghost". Luigi, having a fear of ghosts, sucks E. Gadd up with the Poltergust 3000.