X-Men: Apocalypse (2016)
>Wolverine and Mystique would originally work together to rescue endangered mutants, leading to Charles Xavier recruiting Wolverine to train the young X-Men.
>Professor X would originally become the fouth Horseman after being corrupted by Apocalypse, but the concept was abandoned after Pyslocke was added.
>Taron Egerton was offered the role of Cyclops, but declined. Jamie Blackley, Charlie Rowe, Timothee Chalamet and Ben Hardy auditioned before Tye Sheridan was cast. Hardy was later cast as Archangel.
>Chloe Moretz, Hailee Steinfeld and Elle Fanning auditioned for Jean Grey before Sophie Turner was cast.
>Amber Stevens and Zendaya auditioned for Storm before Alexandra Shipp was cast.
>Tom Hardy and Idris Elba were approached for Apocalypse before Oscar Isaac was cast.
>Although the Weapon X segment were always part of the movie, Wolverine's breakout was added in reshoots.
>The Quicksilver rescue segment was planned out with Michael Jackson's "Beat It" in mind, but Fox couldn't secure the rights to include the song in the movie and replaced it with Eurythmics's "Sweet Dreams".