When Dexter goes to acquire his drugs for the tranquilizers he uses the name Patrick Bateman. Anyone aware of this name will know this person to be the protagonist in American Psycho.
Seeing that Dexter follows Harry's Code, and Dexter does not generally solicit sex, did Michael Cuesta (or James Manos, Jr. whoever introduced it) want to hint at anything about this? What would it have for him to use such a violent out of control character as Dexter's fake name?