Both the Marvel and DC comic book universes labor at continuity. Events in one comic book impact others. Large cross-over events determine plot lines across multiple titles. A shared set of rules more stringent than genre conventions limit and explain what can and can’t happen. Golden age comic stories tended to episodic. The events of one story seldom mattered much for a subsequent story. Storylines from one title seldom if ever effected another. Nor did titles produced by a publisher share conventions about things like alternate realities, time travel, how super hero powers work, magic, etc. When did the big 2 comic publishers start producing stories in self-consistent “universes”? Did the rise of fan communities play a role in this transition?