You control a young boy called Johnny Burger who plans to visit his cousin Emanuel for two weeks. As he arrives he finds him gone. A scientist, who's also looking for Johnny's cousin, comes by and offers Johnny 500DM (Deutsche Mark) for an experiment.
Of course, the experiment goes awry. During the procedure a mysterious guy flashes the scientist's memory. The emerging irritation causes the professor to start pushing random buttons, which results in Johnny's transformation as a human pig. After Johnny wakes up the professor is gone, too, as he was kidnapped to the Planet Ladea.
So, Johnny's quest comprises of finding the professor to be transformed back into a normal state and finding out what happened to Emanuel.
Mutation of J.B. plays like a usual Point 'n Click comic adventure. At the bottom of the screen you find a selection of commands in German ("Go to", "Talk to", "Look at", "Use", "Take") and your inventory that stores all collected items. The game doesn't include English subtitles.