Trivia: When all the Avengers are attempting to lift Thor's hammer, Captain America is able to move it slightly. In the comics, Cap is one of the few characters noble enough to be able to lift Thor's hammer (notable others being Storm and Beta Ray Bill).
Trivia: When Tony Stark is choosing FRIDAY as his AI companion, there's a card labeled JOCASTA. Jocasta, in the comics, is a robot, member of Avengers, and was created by Ultron. (01:36:55)
Trivia: Stan Lee makes his customary appearance whilst the Avengers and a load of War Veterans are enjoying a get together. Thor offers a 1,000 year old Asgardian drink to Captain America, and Stan Lee asks for some. (00:25:15)
Trivia: Aaron Taylor-Johnson was apprehensive about joining the cast due to Marvel's intense contracts and schedules. Even after signing on, he was extremely nervous. It wasn't until he found out his character's twin sister was being played by Elizabeth Olsen that he calmed down and really got excited about the project, as they are close friends and had previously played husband and wife in 2014's "Godzilla."
Trivia: Unlike previous movies in the Marvel franchise, there is only one credits extra, and that's in the middle, featuring Thanos and the Infinity Gauntlet.
Trivia: Scarlett Johanasson was pregnant during filming, and thus had to rely on stunt-doubles moreso than usual. Amusingly, the three stunt-doubled hired to cover for her resembled her so greatly, the cast often would mistake the doubles for her and try to have conversations about the scenes and filming, only to realise they were talking to the "wrong" Black Widow.
Trivia: Near the end of the film, the Vision saves the Scarlet Witch, a possible foreshadowing of the beginning of their romantic relationship from the comics. These characters were married for a long time in the pages of the Avengers and even temporarily had children (it's complicated).
Trivia: Wakanda is the home country of Black Panther, another Marvel character, due to appear in Captain America: Civil War.
Trivia: Hawkeye's "Nobody would know" line was ad-libbed by Jeremy Renner.
Trivia: The SHIELD technician on board the Helicarrier at the end of the movie (who announces the lifeboats taking off) also appeared in Captain America: The Winter Soldier as the SHIELD agent who refused to send out the Insight Helicarriers and was threatened by Rumlow.
Trivia: The title does not appear until twelve minutes into the film.
Trivia: The Hulk does not have a single word of dialogue in the film.
Trivia: Joss Whedon desperately wanted to have a surprise cameo by upcoming Marvel Cinematic Universe heroes Captain Marvel and especially Spider-Man (who he had just learned was going to be rejoining Marvel) during the final scene where we see the new Avengers assembling to train, but he was unable to for time and logistics reasons.
Chosen answer: This is a fairly US-centric gag. In Archie comics, the titular Archie has two competing love interests: Betty and Veronica. Given the Hulk/Banner's history with Betty Ross being able to calm him down, Tony Stark has named the containment system/Hulkbuster armor "Veronica".