Given the money invested in Marvel's tentpole franchise, there is a level of interest in the production process for all of the movies that should be considered pretty unprecedented. It's now got to the point that secrets and spoilers are kept under such tight security that only a careless cast member who just doesn't give a damn can really spoil anything now. Or the LEGO tie-ins.
It's frustrating not knowing things, but to a certain extent, it's better not to know. Likewise, we should try and wait until after these movies are released before we start looking into what could have been. And while alternate and deleted scenes are all very interesting, it's the missed opportunities to see whole new characters that really stick out as most interesting.
Even the most packed ensembles in the MCU at one point had other hero and villain faces involved and thanks to our obsession with knowing about every brushstroke in the creation process, there are some big ones we already know about.
So what could have been?
10. Captain Marvel - Avengers: Age Of Ultron
The Original Plan
She might have debuted in the MCU in 2019, after a brief tease in Infinity War's post-credits scene, but Captain Marvel almost turned up a lot sooner in the MCU. Joss Whedon apparently wanted to add her to the mix for Avengers: Age Of Ultron when he was putting the script together.
He even went as far as shooting some test footage, with Kevin Feige confirming that the director had included FX plates of Captain Marvel flying at the end of the movie in the scene showing Captain America and Black Widow putting together the New Avengers team.
Why She Was Cut
The plan was to simply cast her at a later stage when Whedon included the shots of her, but Kevin Feige later revealed why she was dropped:
"...It would have done that character a disservice, to meet her fully formed, in a costume and part of the Avengers already when 99% of the audience would go, ‘Who is that?’ It’s just not the way we’ve done it before."
Instead, Danvers was replaced with Scarlet Witch in the scene below at 02:23...