Frank the Doorman caused a building full of humans to fall asleep so that a Mare could invade their dreams.
In central and northern European folklore, the Sandman is a mythical character in many children's stories. He is said to sprinkle sand, or dust, on or into the eyes of a child at night to bring on dreams and sleep. The grit or "sleep" in one's eyes upon waking is supposed to be the result of the Sandman's work the previous evening. The Sandman is frequently referenced in popular culture.