One of the weapons Marvel used in its climb to comic-book dominance was a willingness to invent new characters at a dizzying speed. There are so many Marvel universes, indeed, that some superheroes do not even exist in one another's worlds, preventing gridlock.
Roger Ebert (2012). “Roger Ebert's Movie Yearbook 2013: 25th Anniversary Edition”, p.33, Andrews McMeel Publishing
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