1.First, Wasp was originally going to be the central female superhero in The Avengers instead of Black Widow.
2.In an early draft of Avengers: Age of Ultron, Captain Marvel was going to make an appearance — the cameo was later scrapped because Kevin Feige believed Carol deserved her own origin movie.
3.Tony Stark sitting inside the giant donut at Randy's Donuts was inspired by a suggestion from the IRL shop owner — the owner told director Jon Favereau that he would "really like if [Iron Man] flies through the donut."
4.In every Phase Two Marvel movie there's a nod to Luke losing his hand in Star Wars: The Empire Strikes Back — you can spot a character in each of these movies losing an arm.
5.It took Dave Bautista three to five hours to get into makeup everyday while filming Guardians of the Galaxy — for the sequel, the process went down to only 90 minutes.
6.Due to the fact that the cast of Infinity War was so big, the entire cast never actually saw each other on set — they would bring in a small group of actors to shoot one scene, those people would leave, and then a new group would be brought to set.
8.Iron Mannever had a full script, they only had an outline when filming began — the final product was mostly made up of improvised moments from the cast.
9.During scenes where Jane and Thor kissed, Natalie Portman was actually standing on a high ramp in order to reach Chris Hemsworth — Natalie is almost a foot shorter than Chris IRL.
10.In Black Panther, the fight scene in the club with T'Challa, Okoye, and Nakia was one of the first scenes filmed for the movie.
11.When creating the character of Killmonger, director Ryan Coogler was inspired by Batman and The Joker's dynamic — he wanted audiences to believe that the hero might not win.
12.Joss Whedon originally wanted to introduce a second villain in The Avengers — he thought Loki wasn't big enough on his own.
13.In Thor: Ragnarok, the "He's a friend from work!" line was actually improvised by a kid who was visiting the set that day.
14.Also, before filming began on Thor: Ragnarok, Cate Blanchett actually looked up Hela makeup tutorials on YouTube in order to better understand her character.
15.While preparing for the role of Carol Danvers in Captain Marvel, Brie Larson actually trained with several real-life Air Force Thunderbirds.
16.Baby Groot's dancing scene in the beginning of Guardians of the Galaxy Vol. 2took nearly two years to put together.
17.For Captain America: The First Avenger, Sebastian Stan originally auditioned for the role of Steve Rogers — eventually, he fell in love with Bucky because of his character arc.
18.While preparing to play Peter Parker in Spider-Man: Homecoming, Tom Holland actually enrolled in a high school in the Bronx.
19.Originally, Maya Hansen was going to be a major villain in Iron Man 3 and have a much bigger role opposite Aldrich Killian — her role was reportedly reduced due to Marvel's fear that female toys would not sell.
20.Due to the fact that 20th Century Fox owned the rights to the X-Men, Quicksilver and Scarlet Witch were legally not allowed to be referred to as mutants in Age of Ultron.
21.In Thor, Chris Hemsworth improvised the line "another!" and smashing his coffee mug on the ground.
22.There was very little CGI used in Captain America: The Winter Soldier. In fact, one sequence that was 100% authentic was Falcon jumping out of a plane in slow motion.
23.In Thor: The Dark World, Thor's hammer is actually 10% larger than the one he used in the original Thor — the new design was a combo of the hammer from Thor and The Avengers.