So I finally did it, I now have a Marvel Avengers post! I know, about time! I got these bits of trivia and facts from IMDB.com. There's some interesting ones if you're a fan of Buffy the Vampire Slayer as well!
1. Robert Downey Jr. kept food hidden all over the lab set and apparently nobody could find where it was, so they just let him continue doing it. In the movie, that's his actual food he's offering and when he was eating, it wasn't scripted. He was just hungry.
2. To prepare for the role of Agent Clint Barton (Hawkeye), Jeremy Renner was trained by Olympic archers.
3. After Thor takes Loki off the Quinjet down on the mountain side, two large ravens fly by them as they are talking. In Norse mythology, their father, Odin, had two ravens, Huginn and Muninn, who would bring Odin information from Midgard (Earth).
4. According to director Joss Whedon, the original cut of the movie was over 3 hours long. About 30 minutes of the excised footage are included on the Blu-ray, most of which revolves around Steve Rogers (Captain America) struggling to adjust to the modern world. Chris Evans has since announced that these deleted scenes will be used for Captain America: The Winter Soldier (2014).
5. Chris Evans was unsure about his character's line, "I understood that reference!" because he was worried that it would make audiences think that his character was unintelligent. However he was quickly comforted after he watched the movie with an audience and he saw that they found the line humorous as opposed to stupid.
6. Clint Barton (Hawkeye) is an ambidextrous archer (although Jeremy Renner is left handed). He is seen shooting right-handed in Thor (2011) and both left-handed and right-handed in this film.
7. Samuel L. Jackson's role as Nick Fury in this film makes him the second actor (after Hugh Jackman, who has appeared in all the X-men movies) to play the same comic book superhero in five different movies.
8. Joss Whedon explained that two of the founding Avengers members Ant-Man and Wasp were cut from the script because the film had too many characters.
9. After Loki is brought on board the Helicarrier, Tony Stark can be seen wearing a Black Sabbath T-shirt. Black Sabbath is better known for their song "Iron Man." Although the song was not originally associated with the Marvel Comics character, it has since been referenced in the comics and the end of Iron Man (2008) when Tony quotes the lyric, "I am Iron Man."
10. When Natasha Romanoff and Bruce Banner are blasted to a lower deck of the Helicarrier, it triggers Banner's transformation into the Hulk. As he is transforming, he falls from a platform to the floor. On the floor is painted "WARNING CONTENTS UNDER PRESSURE" with small arrows, which happen to be pointing to Banner.
11. According to Joss Whedon's commentary, Bruce Banner's saying of Loki, "You can smell crazy on him", was a setup for when the Hulk faces off against Loki in Stark Tower. Originally, Loki was going to make multiple versions of himself and the only way the Hulk was going to discern where Loki was to smell them. Only the real Loki would have a scent.
12. The shocked expression of Loki after being slammed by Hulk was created by animation director Marc Chu shaking Tom Hiddleston violently and repeatedly.
13. Samuel L. Jackson's Nick Fury is from the Ultimate Marvel Universe created in 2000 to re-imagine and update the Marvel heroes for the 21st century. Fury's likeness was actually based on Jackson, who gave Marvel permission to do so. Subsequently, based on that likeness and his star power, Jackson was cast as Fury for all Marvel superhero films owned by Marvel/Disney starting with Iron Man (2008).
14. The laboratory scene where Bruce Banner explains how he once attempted to commit suicide by shooting himself in the mouth is a direct reference to a deleted scene from The Incredible Hulk (2008) where Edward Norton's Bruce Banner tried to commit suicide in this manner out in the middle of Alaska's wilderness only to be stopped by his transformation into the Hulk.
15. After Iron Man flies through a Leviathan, he can be seen crashing on the ground in front of the Shawarma Palace, the which later appeared in a post-credits scene.
16. Alyson Hannigan from Joss Whedon's Buffy the Vampire Slayer (1997) (and wife of Alexis Denisof, who plays The Other in the film), recommended her How I Met Your Mother (2005) co-star Cobie Smulders for the part of Maria Hill.
17. Originally Joss Whedon had not intended the film to include supporting characters from the heroes' individual films, reasoning "You need to separate the characters from their support systems in order to create the isolation you need for a team." However, he eventually decided to cast Stellan Skarsgård, Paul Bettany and Gwyneth Paltrow (Paltrow was cast at Robert Downey Jr.'s insistence).
18. Tom Hiddleston revealed in an interview with the Guardian that the code name for the film early in its production was 'Group Hug'.
19. Tony Stark tells Bruce Banner that he admires his work on anti-electron collisions. When electrons and anti-electrons (also known as positrons) collide, they annihilate each other and high-energy photons or gamma rays (the fictional means by which Bruce Banner became The Hulk) are produced in their place.
20. The sound editor Christopher Boyes has stated that he went through a complicated process to craft the Hulk's voice. The final product "turned out to be [a combination of] Mark Ruffalo, some Lou Ferrigno and a little bit of me and two people from New Zealand."
21. According to Joss Whedon, the film is strongly influenced by the early 1960s Avengers comics, which he was a fan of while growing up: "In those comics these people shouldn't be in the same room let alone on the same team - and that is the definition of family."
22. Mark Ruffalo claims to be the only actor to date (2012) to play both The Hulk and Bruce Banner in the same movie. Technically, both Eric Bana and Edward Norton have done motion capture work for their respective Hulks, but Ruffalo is the first actor to perform the Hulk live on set via performance capture.
23. According to Joss Whedon, the arrangement of the monitors on the helicarrier bridge were arranged to resemble the wings of the SHIELD logo. The eagle head can actually be seen at the foot of the conference round table at the end of the film when repairs are being made.
24. Robert Downey Jr. initially pushed Joss Whedon to make Tony Stark the lead: "I said, I need to be in the opening sequence, Tony needs to drive this thing. He was like, okay, let's try that. We tried it... and it didn't work, because this is a different sort of thing, everybody is just an arm of the octopus."
25. Robert Downey Jr. thought the scene when Iron Man regains consciousness could use a little snappier dialogue, so he requested that Joss Whedon add some. One of the ones that made the cut (the Shawarma reference) is influenced by Nicholas Brendon's (Xander from Buffy the Vampire Slayer) interview. Nicholas mentions, 'Would anyone like to go get some Shawarma?'.
26. Loki is described as being a king in the world from which he came. Shortly after this when The Avengers ask for Loki's location in Germany, Loki is said to be at "22 Königstrasse", meaning 22 King Street.
27. The female superhero Wasp was included in an early draft of the script. She was however replaced with the already-existing Black Widow.
28. Thor spends most of this movie in his Asgardian armor but with bare arms, a nod to his early appearances in the comics. During his time on the Helicarrier, he is also seen without his cape, an allusion to his Ultimate Comics appearance.
29. In order to create a total extraterrestrial look for the Chitauri, they have four thumbs, two on each hand. This can be seen when Loki (Tom Hiddleston) is talking with The Other (Alexis Denisof).
30. Tony Stark describes his group as "Earth's mightiest heroes, that kind of thing." This refers to the bold label that has appeared on "The Avengers" comic books since its 1963 publication. The phrase has also been used as the subtitle for The Avengers: Earth's Mightiest Heroes (2010), the most recent animated series before the live-action Avengers film.
31. One of the cards in Agent Coulson's Captain America card set is a reproduction of Captain America's first comic book appearance where he punches out Adolf Hitler.
32. Captain America finds Phase 2 weaponry in the secure storage area of the helicarrier. Those weapons are emblazoned with the Hydra logo.
33. The CGI Hulk's body was modeled after Long Island bodybuilder and male stripper Steve Romm, while the Hulk's face was modeled after Mark Ruffalo.
34. The code name for The Avengers release to theaters is Team Building.
35. Captain America's shield is scratched in the film. In the comics, his shield is made of an adamantium/vibranium alloy and can only be damaged on a molecular level.