Following in the footsteps of Captain America: The First Avenger, Captain Marvel, the penultimate movie of the Marvel Cinematic Universe's Phase Three, will be a period piece. Audiences will meet Brie Larson's Carol Danvers during the 1990s, a time when the public superhero craze hasn't spread around yet. While Carol will obviously be the star of the show, supposedly she won't be the only superhero who shows up, as it's being reported that we'll see Mar-Vell, the original Captain Marvel (well, from Marvel Comics, anyway).
Following the announcement at San Diego Comic-Con of Captain Marvel being set in the '90s and that the Skrulls would be the main antagonists, Marvel Studios Kevin Feige revealed that the movie would lean into the mythology of the Kree-Skrull War. The Kree have already appeared in Guardians of the Galaxy and a few Agents of S.H.I.E.L.D. episodes, and now the word is that we'll see one of the species' greatest heroes appear in Captain Marvel. According to MCU Exchange, Mar-Vell will play a key role in Carol Danvers' origin story just like in the comics, and the Psych-Magnetron accident will be used to show how she obtains her powers. The outlet also notes that Carol's DNA becoming half human/half Kree will be used to explain why she's aged so slowly (or not at all) when she eventually shows up in the present day MCU.
Mar-Vell was introduced to the comics in 1967's Marvel Super-Heroes \#12. Shortly after the Kree first encountered humanity, he was sent to Earth as a spy, and he took the identity of the recently deceased Dr. Walter Lawson (no word yet on if that guise will be used in Captain Marvel). However, as Mar-Vell started protecting the people of Earth, he grew attached to them, to the point that he was eventually charged with treason by the Kree Empire. From that point forward, he fully became a cosmic superhero for all, and later on he used the Nega-Bands to provide him with more abilities. Sadly, Mar-Vell died from cancer that came from exposure to a nerve gas years earlier.
After a few appearances in animated TV shows and video games, Captain Marvel marks his live action debut, although it was briefly rumored during Guardians of the Galaxy Vol. 2's production that Mar-Vell would be used as Peter Quill's father. That was quickly debunked by director James Gunn, and Ego the Living Planet ended up being the one saddled with the parental duties. Despite Captain Marvel co-writer Nicole Perlman previously saying that Carol Danvers' origin story would be altered so it wouldn't resemble Green Lantern's as much, if this report proves to be legitimate, than we can still count on Mar-Vell crossing paths with her and remaining a positive figure in her life.
Captain Marvel flies into theaters on March 6, 2018.