In reality, the Shaggy dog was a teenager named Wilby Daniels (Tommy Kirk) who had been changed into a canine when he spoke a magical Borgia spell "In Canis Corpore Transmuto" that was inscribed on an amulet. In order to be released from this spell, Wilby had to perform an heroic act.

A number of sequel films rehashed this tale of a shape-shifting teen. They included: The Shaggy D.A. (1976) starring Dean Jones; the made-for-TV movie The Return of the Shaggy Dog (1987); the made-for-TV movie The Shaggy Dog (1994); and feature film remake The Shaggy Dog, (2005) with Tim Allen (of HOME IMPROVEMENT fame).

A dog named Sammy's Shadow played the role of The Shaggy Dog in the original film.

Annette Funicello, The Shaggy Dog and Tommy Kirk