Dr. Jekyll and Mr. Hyde

A public domain piece of fiction about a scientist who creates a potion that changes him from scientist to murderer. In the original story the transformation caused the good doctor’s memory to be suppressed while Hyde was in control. You had an Ego based Scientist and an Id based madman.

This idea birthed a lot of derivative works. Also make it sexier.

In the TV show Family Matters, the needy Urkel uses a serum and transformation chamber to turn into the suave Stephan.

In film this has also been extended to men transforming into women. With a variety of Dr Jekyl and Miss/Sister Hyde stories.

Most commonly the transformed doesn’t know what their other half is doing, but they know they exist. Throw in a scene where the transformed goes on a shopping spree for new clothes as well as a scene where the Dr Jekyll ties themselves up to something show themselves transform to Hyde in front of a loved one.

Typically Hyde is everything that Jekyll is not. The most erotic versions show this as being overly confident and dripping with seduction. But also Hyde is a criminal not limited by Jekyll’s morals.

Almost never do Hyde and Jekyll work together.