Janus is the Roman god of “beginnings, gates, transitions, doorways, time, and doors”.
In his classical representation Janus has two faces: one turned toward the past, the other toward the future. “Janus presided over the beginning and ending of conflict, and hence war and peace. The doors of his temple were open in time of war, and closed to mark the peace. As a god of transitions, he had functions pertaining to birth and to journeys and exchange, and in his association with Portunus, a similar harbor and gateway god, he was concerned with travelling, trading and shipping.”
“In Act I Scene 2 of Shakespeare’s Othello, Iago invokes the name of Janus after the failure of his premiere plot to undo the titular character. As the story’s primary agent of change, it’s fitting that Iago align himself with Janus. His schemes prompt the beginning of each of the main characters’ ends: in his absence, Othello and Desdemona would likely have remained married and Cassio would have remained in his respected position of power. Iago guides (if not forces) the story through inception, climax, and finale. Furthermore, Janus’ common two-faced depiction is the perfect visual metaphor for Iago’s character. Othello’s characters believe him to have only the best of intentions, even going as far as to call him “honest Iago,” completely unaware that he spends every unwatched second plotting their undoing. He appears selfless and compassionate but, in truth, is power-hungry, amoral, and without regard for the well-being of others.”
In James Bond movie GoldenEye, agent 006 calls himself Janus after faking his death.
In season 2, episode six of Buffy the Vampire Slayer, one of the episode’s antagonists, “a chaos worshipper,” is seen praying to a statue of the god.
The Resident Evil series of movies loosely based on the popular game franchise of the same name’s amnesiac lead character of Alice has been identified as previously having gone under the name “Janus Prospero”.
The Buffy: The Vampire Slayer episode “Halloween” has Ethan Rayne using a ritual dedicated to Janus to trigger the spell that transforms anyone wearing costume pieces bought at his story into the characters they dressed as.
In The Castle in the Attic, a medallion with the image of Janus is used to magically shrink and enlarge characters, and is a major plot point.
In Utopia (UK TV series), Janus is the name of method of population control hidden within the manuscript, a major plot point.”
(abstracts from Wikipedia article on Janus)