Transformations

When Alan Moore started to write Marvelman, later Miracleman, MM learned that all of his previous adventures had occurred inside a virtual reality.

When Moore started to write The Saga of the Swamp Thing, Swampy learned that he was not a man who had become a plant but a plant that thought that it had been a man.

In both cases, the entire basis of the series was completely transformed. And the transformations continued. MM's powers made him a benevolent global dictator, regarded as God. Swampy learned, thanks to John Constantine's intervention, that the passage of a man through fire and his transformation into a swamp plant is the first stage in the genesis of the next plant elemental, the guardian of the Terrestrial ecology. The elemental has powers that make him a nature god although Swampy had not suspected that he had such powers before he was written by Alan Moore.

MM changes the world. Swampy can change the world by transforming deserts into plains and forests but decides that it would be wrong to interfere in evolution in this way. The difference is that MM has his own continuity whereas Swampy must conform to DC Comics continuity where the pretense is that the world remains essentially unchanged despite the presence in it of powerful beings like Superman, other superheroes and the Swamp Thing.

In Watchmen, Doctor Manhattan and Ozymandias change the world because, although this group of characters began as the Charlton Comics superheroes who were incorporated into DC continuity, Moore was able to transform them into the Watchmen with their own continuity.