Stay Puft Marshmallow Man

The Staypuft Marshmallow Man was originally the vessel used by Gozer to destroy the world in Ghostbusters but became a ghost in its own right shortly afterwards (despite having been blasted in the film).

The Staypuft Marshmallow Man has varied in the series from a villain to a hero but rarely displayed the same level of malevolence as it did in the original movie - perhaps due to the fact that it was no longer fully controlled by Gozer.