The Stay Puft Marshmallow Man is a fictional mascot from the Ghostbusters franchise of media, which sometimes appears as a giant, lumbering paranormal monster. It becomes the physical manifestation of the Sumerian demonic deity Gozer. It first appears in the 1984 film Ghostbusters

Ghostbusters

Ghostbusters is a 1984 American science fiction comedy film directed by Ivan Reitman and written by Dan Aykroyd and Harold Ramis. The film stars Bill Murray, Dan Aykroyd, Sigourney Weaver, Harold Ramis, and Rick Moranis and follows three eccentric parapsychologists in New York City, who start a...

as a picture logo on a prop package of marshmallows in Dana Barrett's apartment when she places the groceries on her kitchen counter, on a graffiti advertisement on the building next to the Ghostbuster's HQ when the ghosts are released from the containment grid after the power is shut down, then later in the climax of the film.