Pantheistic solipsism is a technical term that has been advanced for the World as Myth idea proposed by science fiction writer Robert A. Heinlein in several of his books and stories, although the concept has little in common with either Pantheism (the universe is God) or Solipsism (nothing exists but my mind).
The World as Myth idea involves the portrayal of all myths and fictional universes existing as parallel universes to our own and that persons and beings from these various “worlds” interact with one another.
For instance, in his last novels, Heinlein’s characters actually travel to and interact with the Land of Oz. Even our own world is considered an alternate (coded as "One Small Step" for the first words spoken on the moon by Neil Armstrong).
Pantheistic solipsism is featured in the work of many other authors. It plays a significant part in Douglas Adams's novel The Long Dark Tea-Time of the Soul. Adams's characters travel to and interact with a variety of Norse Gods in Asgard (among other interconnected events). Dan Simmons's novel Olympos relies heavily on Pantheistic solipsism as a plot device. The Dark Tower series by Stephen King also contains some aspects of Pantheistic solipsism. American Gods and the Sandman comic book series by Neil Gaiman featured a vast number of mythological and newly created gods and creatures interacting with one another. It is unclear whether these other authors were influenced by Heinlein or merely arrived at the same place for their own reasons.
The Sandman is only one example of how pantheistic solipsism has become increasingly popular in contemporary comic books. Series such as Stargate SG-1, Hellboy, Fables, Lucifer, League of Extraordinary Gentlemen, Harry Kipling, "Silver Surfer" and Top 10 are all based on the concept of characters from disparate mythologies interacting with one another. The tendency of popular comics to concoct "crossovers," in which characters owned by different companies interact, is another element of this idea in comics publishing.
It also plays a central role in much of fan fiction, which often features fictional worlds crossing over into the real world and each other.
Pantheistic Solipsism is the basis for the plot of the Arnold Schwarzenegger film The Last Action Hero in which a character in an action movie crosses into the "real world". Stranger Than Fiction also bases its plot on Pantheistic Solipsism. In that movie, the main character (Harold Crick) finds that his life has become the subject of some narration and the he has somehow become a main character of a story. In a similar example, the movie Pleasantville features a pair of teenagers who stumble into a reality based on a popular 1950's television show.
In the real time strategy game, Age of Mythology, pantheistic solipsism is the basis for the game's story, as players control heroes who interact with gods and mythical creatures from Norse, Egyptian and Greek pantheons and myths. Starting on Atlantis, the plot follows a cyclops who tries to resurrect the Titans and bring Ragnarok. The player cooperating with these three civilisations, must summon Zeus, Osiris and Thor to prevent this.