The best thing about shows based on comic book is sometimes you can create a brand new character, and yet they fit right in. This definitely fits what Puppet King was.
Though he was a literal one-time-only villain, he made his mark. He was able to trap the souls of the Titans into puppets he made of them, giving him control of their real-life bodies. This causes a "freaky friday" situation with Starfire and Raven where their souls switched bodies.
He was quite a threat, and even tried to kill the Titans puppets (souls still inside) so he could forever control their real bodies. Only once the controller was destroyed did everything return to normal, and Puppet King was no more.