Unlike the other Groening cartoons, all of the human characters in this series have five fingers on their hands. The mythical creatures, such as Elfo, have only four, and the demon and Bean's stepmother have three fingers.
In Sky Gundersons airship, when Tiabeanie is searching for the little black book, she opens a drawer with "assorted lengths of wire" in the first episode of futurama the professor refers to his drawer full of "assorted lengths of wire." Although different colors, theyre all the same shape and lengths in both episodes.
Luci's design is inspired by the minions of Hades from the animated Disney short The Goddess of Spring from 1934.
Elfo is based on the first character Matt Groening drew after he had established his signature character style for drawing faces.