First and most importantly, Stephen King does not appear in this episode. He doesn't know about this episode, and is in no way affiliated with this episode, L.A. Kessler, the Genesis series, Lisa Kessler or any of her other novels.
We call it the Stephen King Connection because, unlike Lisa's paranormal romance novels, Stephen King's works were the inspiration for Perfect, and without him, this book would probably not exist. Lisa talks about that, and how specific Stephen King horror novels inspired Perfect. She also reads a passage from the forthcoming thriller to further illustrate how those horror novels shaped this particular story.