Regarding the relationship to the vampire narrative: I think that King has taken the vampire narrative and flipped it on it's head. In fact, all the well-known aspects of the vampire legends apply equally well to sleepwalkers, EXCEPT OPPOSITE!
For example:
Vampires can't be seen in mirrors; sleepwalkers can ONLY BE SEEN IN MIRRORS!
What's the opposite of a wooden stake through the heart? Answer: A cat scratch on the back.
Vampires transform into bats; sleepwalkers transform INTO CATS!
The vampire bat's preferred mode of transportation is flight, whereas sleepwalkers prefer to drive a Trans Am.
Vampires must be explicitly invited into the home of their victim; sleepwalkers invite their victim into their home, then give the victim a flower, and then tell the victim to leave.
Vampires use "glamouring" to hypnotize their victims, sleepwalkers just hit on them at the movie theater.
Pretty convincing evidence that sleepwalkers are vampire opposites if you ask me!
