Scooby-Doo and Scrappy-Doo (1979)

S4E13 Who's Scooby-Doo?

At a Science Fair, Scooby and Shaggy accidentally end up switching bodies after using an experimental machine. Unfortunately, their predicament worsens when the device is stolen, leaving them unable to return to their original forms. Determined to regain their identities, the duo embarks on a comical adventure to track down the thief and retrieve the machine before it’s too late.