DC Comics is an American comic book publisher best known for its superhero stories featuring characters including Batman, Superman, and Wonder Woman. The company debuted in February 1935 with "New Fun: The Big Comic Magazine". Most of DC's comic books (as well as some published under its imprints Vertigo and Young Animal) take place within a shared universe called the DC Universe (DCU) allowing plot elements, characters, and settings to cross over with each other. The concept of the DCU has provided DC's writers some challenges in maintaining continuity, due to conflicting events within different comics that need to reflect the shared nature of the universe. "The Flash of Two Worlds" from "The Flash" #123 (September 1961), which featured Barry Allen (the Silver Age Flash) teaming up with Jay Garrick (the Golden Age Flash) was the first DC comic to suggest that the DCU was a part of a multiverse.