The current version of Captain Marvel currently in theaters is not the original Captain Marvel, a superhero whose comics once outsold Superman's.

Here's the surprising comic book history behind two current superhero movie stars who share the same name...sort of.

In 1939, writer Bill Parker and artist C.C. Beck created a character they wanted to call 'Captain Thunder.' Because every publishing company was trying to cash in on the success of the superhero comic book launched with Superman in 1938, new superheroes were being created at, well, super speed. This meant that another company was already using the name 'Captain Thunder.' Parker and Beck's editor suggested the name 'Captain Marvel.' This was decades before Marvel Comics existed, of course.

Captain Marvel was the heroic alter ego of young Billy Batson, who would shout the magic word 'Shazam' to transform into an adult hero with the wisdom of Solomon, the strength of Hercules, the stamina of Atlas, the power of Zeus, the courage of Achilles, and the speed of Mercy. The acronym for these names was where the name 'SHAZAM' was derived.

Captain Marvel was a huge success for publisher Fawcett Comics, even outselling Superman to become the most popular superhero of the 1940s. Captain Marvel was also the very first superhero to get his own movie, The Adventures of Shazam serial in 1941. Things looked bright for the character until the superhero comics began to lose popularity in the 1950s and National Comics (future DC Comics) sued Fawcett. They claimed Captain Marvel was too similar to Superman. Fawcett settled out of court and eventually gave up trying to publish Captain Marvel comics, licensing the character and his supporting cast to National.

When the late Stan Lee and Jack Kirby decided to create a new line of comics to compete with the success of DC's Justice League, they decided to name their new brand of superhero comics 'Marvel Comics.' The name soon became the name of the company, which trademarked its own Captain Marvel in 1967, an alien superhero also created by Lee and Kirby.

In the early 70s, DC decided it wanted to use its version of Captain Marvel, but could only refer to the character as Captain Marvel within the pages of a comic book or other work of fiction. They decided to simply call the character 'Shazam,' though he is still known today by comic book fans as the original Captain Marvel. He finally gets a new movie, also titled 'Shazam,' April 5th.