The future of the Marvel Cinematic Universe is shaping up to be an interesting one. With Iron Man and Captain America seemingly gone for good, Phase 4 of the MCU will look much different than its predecessors. In addition to franchise regulars like Black Widow and Doctor Strange getting the spotlight, new characters like Shang-Chi and The Eternals will be introduced in the next few years. We will also be getting long-awaited sequels to Black Panther, Captain Marvel and Spider-Man: Far From Home. The latter two are particularly interesting because both Captain Marvel and Spider-Man were originally intended to appear much earlier in the MCU.
Back in 2015, when Avengers: Age of Ultron was about to hit theaters, director Joss Whedon was answering questions on the press tour about the film's many heroes. In an interview with Empire, Whedon explained that he originally intended to have both Captain Marvel and Spider-Man appear in the final act of the film:
"I wanted all those people. I said, it would be great if we could just add a few more, if we could have a Captain Marvel there, that you’ve made a deal for. And they talked about it. I was like, ‘And Spider-Man, we could do that too, cause Sony had approached us during the first movie about a little integration."
Whedon even went as far as to shoot FX plates for the film in which Captain Marvel would have flown to Avengers HQ at the end of the film, joining the remaining heroes in the hanger during the last scene. Ultimately, Captain Marvel's cameo was cut and the final shot replaced her with Scarlett Witch, and Spider-Man was nowhere to be found.
Marvel Studios president Kevin Feige explained that Captain Marvel was cut from the film because it would have done the character a disservice to introduce her at the last minute and not give her a proper origin story, especially since the part had not been cast yet. The reason for Spider-Man's absence, however, was more due to improper timing. Though the Sony/Marvel Spider-Man production deal was finalized in February 2015, three months before Age of Ultron released, it would have been too much to add scenes at the last minute to include the wall-crawler.
But all hope was not lost as both heroes eventually go on to interact with Earth's Mightiest Heroes. Spider-Man got recruited by Tony Stark to assist him in battling Captain America in Civil War, leading to a now-iconic father-son relationship. Tom Hollan's iteration of the character would go on to have his own successful series within the MCU, with the latest entry, Far From Home, becoming the first Spider-Man film to reach $1 billion at the box office.
Captain Marvel also got her time to shine, coming to the Avenger's aid during the mid-credits scene of her solo film. After Thanos used the Infinity Stones to wipe out half of the universe, Nick Fury pages Carol to come back to Earth to help the team save the universe. She lands on Earth and immediately confronts the mourning heroes.
Looking back at Whedon's comments, and how the MCU panned out, not debuting these two heroes in Age of Ultron was a smart choice. Spider-Man and Captain Marvel's solo films went on to receive positive reviews and become massive box office successes. Not to mention, one of the biggest criticisms of Age of Ultron was that it was too overstuffed. With so many characters and plot threads to juggle at once, the film didn't need any more heroes taking up screen time.