Mr. X is the villain in the Josie and the Pussy Cats episode "X Marks the Spot". He is voiced by John Stephenson.
About Mr. X[]
Mr. X was Professor Isaac Belfour's assistant until the night Mr. X stole the invisibility potion, and used it on himself to start to embark on a life of crime. He later abducted Melody Valentine, Alexander and Alexandra, and demanded that Melody give him the formula for the antidote.