Captain Marvel's suit in Avengers: Endgame was initially going to look much different than the one fans saw in the fourth team-up flick this past spring. Brie Larson filmed her scenes for Endgame before Captain Marvel, which caused a lot of the last-minute changes to the superhero's suit.
Director of Visual Development Andy Park recently noted that he believed the character was going to be wearing the same suit in both films, but the powers-that-be at Marvel Studios eventually realized that Carol Danver's suit probably would have changed during the 30 years between films. Sure, the movies debuted three months apart, but they were separated by decades in the MCU timeline.
"The way it worked was I designed her look first for the Russo brothers for Endgame because she initially filmed her Endgame appearances before her solo film," Park noted, according to Screen Rant. "It was a very odd situation I haven't had in all my years that I've been here, to design a character for one director knowing right away she's going to have her own solo film with a different director.
"So she acted in Endgame with her solo-film costume, and then it was decided later that they wanted a new costume for Endgame, because why would she wear this exact same costume decades later?"Park remembered being approached about making new looks for Captain Marvel's suit. Originally, the designer just weathered the suit from Carol's solo flick, but eventually, the outfit changed, which included breaking up some of the shapes in the suit's design and adding more of the color blue. Obviously Larson wasn't going to return to shoot her scenes in a new getup, as it would have been a process that cost millions of dollars, so the studio used CGI to create a new Endgame uniform over the one the actress originally shot in.
This wasn't too daunting of the cast, especially since Captain Marvel has CGI effects around her most of the time when she's using her powers. A wispy yellow glow accompanies the superhero when she flies and when her suit powers up and down.
Iron Man's suit is almost always entirely CGI, as is the character of the Hulk. Endgame used plenty of CGI, from the costumes, to the elaborate backgrounds and battle sequences that couldn't have been done without it. Some storyboard images for the film also showed a different Quantum Tunnel uniform for Thor, which included his signature cape, but the design never made it into the film.