Not Ghoulty(1959)

His fellow ghosts bring Casper up on charges for breaking the Ghostly Laws ,since he will not scare people, and he loses his ghostly powers. He realizes he needs to do something drastic, so he, disguised as a man, invades a meeting of ghosts planning a scare-campaign, and gives them a taste of their own medicine. He regains his standing in the Ectoplasm Society.