"You know... the Sandman. He's back."
Public Domain"Mr. Sandman" illustration - Credit: Vilhelm Pedersen

This is the first time Dream is referred to as The Sandman, the role from which the series itself takes its name. The original Sandman is a character from Western folklore who made his first literary appearances in stories by Hans Christian Andersen and E.T.A. Hoffman in the early 1800s, but would have been commonly known before that. He was said to sprinkle dream-bringing sand in sleepers' eyes; when you rubbed your eyes in the morning, it was this sand that you were rubbing out. He is usually associated with good dreams, rather than bad.