Shaggy's uncle disappears and leaves Shaggy with a billion dollars, so Shaggy...
Shaggy & Scooby-Doo Get a Clue!
Season 1 Episode 10: Almost Ghosts
In a final attempt to nano-power himself, Phibes uses a new version of the formula developed by his agents --- which promptly turns him into a fluffy, saucer eyed kitten.