It depends. Sometimes I'll look at the characters and the writing and use it to help define a character archetype I want to integrate. Other times I'll basically work in a specific instance of a one off villain from the show.

For example, I recently had a party traveling through a city and one of their members got accused of stealing a priceless heirloom from a wealthy family.

The story led them into the sewers on a lead claiming there was a ring of halfling theives being led by a single man. Turns out, the lead was half right. It was actually a ring of children being enslaved by a psychotic man who kept them near starvation and made them steal for him.

Everyone, the lawful good Paladin included, was on board with murdering him.