At the end of the essay, King mentions he likes to watch the most extreme horror movies because it releases a trap door where he can feed the alligators. The alligators he is referring to are a metaphor for the worst in all humans and the morbid fantasies that lie within each of us.
I recognize terror as the finest emotion and so I will try to terrorize the reader. But if I find that I cannot terrify, I will try to horrify, and if I find that I cannot horrify, I'll go for the gross-out.
