The setting was inspired by Robert A. Heinlein's "Time Enough for Love", wherein galactic colonization is in the style of the American Old West: A few pioneers with drive and primitive tools. The M.U.L.E. itself is based on the idea of the genetically modified animal in Heinlein's novel and given the appearance of a "Star Wars" Imperial Walker. Another Heinlein novel, "The Moon Is a Harsh Mistress", provided the decision to not have any government or external authority. In the game's original designs, land was sold by auction, but this caused a feedback loop in which the wealthiest player had the most land and thus made the most money; thus, the developers created the "land authority" that gives each player a free plot of land each turn.