1. Chris Evans turned down the role of Captain America twice before accepting it, because he initially wasn't comfortable taking on that level of commitment and fame.
2. Iron Man director Jon Favreu insisted that Robert Downey Jr star in it, despite the suggestion being turned down at first.
3. Joss Whedon initially wanted there to be a second villain in Avengers Assemble as he wasn't sure Loki was a big enough villain to go against that many characters. He changed his stance when he realised "it’s about how he gets in their heads – it’s going to be fine".
4. There’s a reference to Black Panther in Iron Man 2, as Wakanda is shown on the map in the background.
5. Both Chris Hemsworth and his brother Liam auditioned for the role of Thor.
6. And Alexander Skarsgård also auditioned for the part, and got as far as even trying on the costume.
7. Jeremy Renner was helped by Olympic archers to prepare for playing Hawkeye.
8. Early drafts of Avengers Assemble featured Wasp instead of Black Widow.
9. Dave Bautista had to spend three to five hours every day in makeup for Guardians of the Galaxy to transform into Drax, but they got this down to 90 minutes during the sequel.
10. Marisa Tomei (Aunt May) and Robert Downey Jr (Iron Man) dated years ago! They were still friends after, and she said he recommended her for the role of Aunt May.
11. The ship in Guardians of the Galaxy is called Milano after Peter Quill’s childhood crush, Alyssa Milano.
12. In every Phase 2 Marvel movie, there's a scene where someone gets their hand or arm cut off. It started as an unintentional tribute to Star Wars, and then became intentional.
13. Tom Holland found out he’d be playing Spider-Man through looking on Instagram.
14. An astrophysicist worked on Doctor Strange by advising on science and philosophy.
15. The soundtrack for the first Guardians of the Galaxy is only the second ever soundtrack to sell over a million copies digitally (the first is Frozen).
16. At first, some of the people overseeing the movie thought putting in '70s music would alienate kids watching the film.
17. They had to use ramps in Thor: The Dark World for kiss scenes between Natalie Portman and Chris Hemsworth because of their height difference.
18. Pre-Avengers, Mark Ruffallo was actually considered to play Hulk in The Incredible Hulk.
19. The “catch up” list Captain America carries with him in The Winter Soldier is different for different countries.
20. Because the characters of Quicksilver and Scarlet Witch belong to the X-Men franchise as well as the Avengers one, they can’t be referred to as mutants, or have their dad Magneto referenced in Avengers: Age of Ultron. So in the film they’re both called “enhanced” and the story of their creation is changed.
21. Before appearing in Doctor Strange, Rachel McAdams was considered years ago for Pepper Potts in Iron Man, but declined.
22. Vin Diesel had his own “Groot script” in GOTG2, which had every "I am Groot" line printed in English so that he knew what the character was actually saying. Only him and the director got to see it.
23. Footage was shot for a Captain Marvel cameo in Avengers: Age of Ultron but it ended up being scrapped because it didn't seem like the right context to introduce her in.
24. In Captain America: Civil War, scenes involving Chris Evans wearing a T-shirt were generally filmed early on in the process, because he'd lose weight during filming as a result of running around in the Captain America suit.
25. There wasn’t actually that much audio processing involved when it came to Baby Groot’s voice for Guardians of the Galaxy 2. Vin Diesel has been impersonating cartoon characters for years and can get his voice pretty high!
26. And it took two years to execute the dancing scene with Baby Groot at the start of the movie.
27. There’s an Arrested Development cameo in Captain America Civil War! The Bluth family stair car appears in the airport scene. The Russo brother who directed the film also directed a number of Arrested Development episodes.
28. The "He's my friend from work!" line in Thor: Ragnarok was suggested by a child from the Make a Wish foundation who was visiting the set that day.
29. The Wakandan language spoken in Captain America: Civil War is Xhosa, an official language of South Africa.
30. Black Panther wasn’t meant to have a big part in Civil War, and wasn’t even going to don a costume, but when they thought they might not be able to get Spider-Man in the film, they beefed up his role. By the time they did get him, they decided to keep Black Panther as a bigger role in the film.
31. Tom Holland hasn't been allowed to read the whole script for Infinity Wars in case he reveals spoilers.