Stay Puft Marshmallow Man

Stay Puft Marshmallow Man (also known as Stay Puft or nicknamed Tubby Soft-Squeeze by Ray and Peter) was the final enemy the Ghostbusters faced in the first Ghostbusters movie. It was Gozer's form for The Destructor, when Ray borrowed the idea by thinking of a "just pop in there" logo for a company.

Ghostbusters
Gozer defiantly told the Ghostbusters to choose the Destructor's form, and Ray Stantz "chose" the Stay Puft Marshmallow Man as that form. Everyone else claimed that they had emptied their minds, but Ray admitted that he tried to think of something totally harmless that could never possibly destroy them. As a child, Ray used to roast Stay Puft Marshmallows over the campfires at Camp Waconda. The Stay Puft Marshmallow Man was simply the mascot character for the Stay Puft brand. His accidental choice resulted in Gozer manifesting himself in the form of a 100-foot-tall killer marshmallow man determined to destroy the Ghostbusters, New York, and the entire world. The Stay Puft Marshmallow Man passed Columbus Circle into the Shandor Building and sent civilians into total panic. He crushed a nearby church before attempting to climb 550 Central Park West. After the Ghostbusters tried to destroy it with their Proton Packs, Stay Puft caught fire and nearly burned the Ghostbusters. As it climbed up the building, the boys then decided to cross their proton streams into the Gozer temple to transfer the particle stream through the entrance portal. Stay Puft made it to the top and narrowly missed catching the Ghostbusters. He watched in horror as the Ghostbusters' streams crossed toward the temple. The Gozer Temple, part of the building, and Stay Puft completely exploded. Abundant marshmallow residue rained down all over the nearby streets, drenching thousands of citizens, and a huge lump fell directly on Walter Peck.

Ghostbusters II
In late 1989,Ray Stantz and Winston Zeddemore "remembered" Stay Puft after performing at a child's birthday party.

Ghostbusters: The Video Game
During the start of the Thanksgiving holiday weekend in 1991, Stay Puft returned to the physical plane. Due to the Cult of Gozer's manipulations with the Mandala, Gozer was able to manifest again. And again, in the form of Stay Puft, this time by sweeping Times Square. Ray wondered why Gozer again assumed the form of the Marshmallow Man, since surely there are more effective forms of world destruction that it could have taken. Ray ends up theorizing that there is "one Destroyer Form per god per dimension", which means that Gozer can only assume this form in the Earth dimension. It is identified as a Class VII Outsider Avatar and a Deity (a supreme being). Due to the complications Gozer faced in penetrating the human realm, the Destroyer Form was not even as powerful as its original incarnation, which would seem to be confirmed by being finally outmatched by the firepower of a single Ghostbuster, the Rookie, who used the Boson Dart, a new feature added to the Proton Pack, against the god. Keeping Puft weaker than it was before may also explain why the Ghostbusters originally planned to trap him in the Ecto-1b's Super Slammer Muon trap.

During his assault of destruction, he demonstrated a new power: the ability to spawn numerous Mini Stay Pufts, minor marshmallow minions formed from his own residue. Gozer tried to capture Ilyssa Selwyn in order to sacrifice her and become stronger, but ultimately failed. Unable to reach its full potential, the Stay Puft Destroyer Form was destroyed, covering all the surrounding buildings and streets in a hot shower of marshmallows. His giant hat also fell on a building, where he was last seen hanging.

The Real Ghostbusters
The Stay Puft Marshmallow Man also appeared in a number of episodes of the Real Ghostbusters cartoon series. Unlike in the film, he was not simply an avatar of Gozer, but was his own entity entirely. He was also not always an antagonist, as in some of his appearances in the show, he would actually help the Ghostbusters fight even greater threats.

Mr. Stay Puft's alignment and intelligence seemed to shift with each episode. When he first appeared in the episode "Cry Uncle", he went on a rampage across New York until being recaptured by the Ghostbusters. In the episodes that followed, he had supposedly been "rehabilitated" and was no longer the savage, angry destroyer he had once been. On one occasion, he helped to save New York by fighting against Murray the Mantis. On other occasions, he was shown to be capable of speech.

Classification
The Stay Puft Marshmallow Man is a Class 7 Outsider Avatar (alternatively a Class 7 Avatar Manifestation in the stylized version of  Ghostbusters: The Video Game ) as evidenced when it was scanned during the Shandor Incident in 1991.

Type
Originally, Stay Puft was believed to be a Deity (supreme being). In his file with the Paranormal Contracts Supervision Commission, Stay Puft is stated to be an entry homunculus with psychokinetic charge and ectoplasmic animation. It was also said that with each formation, Gozer energy signatures were accompanied by physical readings from Stay Puft. More and more latent psychokinetic energy was introduced into the creature to make up for Gozer's deficiencies, so Stay Puft became more and more a separate entity from Gozer. Potentially being animated with energies without any willpower makes Stay Puft more vulnerable to domination by intelligent powers other than Gozer. In theory, ghosts of class 5 and up, which are capable of animating physical mass and attracting P.K.E. latent of the environment could take control of Stay Puft.