Sebastian Stan revealed that the backpack that Bucky is seen wearing in the trailers contains journals that he has put together of his scattered memories.
Tom Hiddleston confessed that even though he did not appear in the film, it contained one of his favorite moments in the Marvel Cinematic Universe, the helicopter scene. He enthused, "I mean Chris Evans does a bicep curl, with a helicopter! If you don't love that, we can't be friends."
The day before filming a fight scene with Robert Downey Jr., Sebastian Stan sent him a video of himself doing intense bicep curls in front of the decapitated head of an Iron Man suit. He attached the message, "Looking forward to our scene tomorrow Robert."
Tom Holland commented on how intimidated he was when he came to screentest for Spider-Man, saying that Robert Downey Jr. took him aside and said, "Listen, I remember my screentest for Iron Man. I remember how terrified I was. Just think of it as an audition. It's nothing too scary. If you get it wrong, we'll just start again. No pressure."
T'Challa had a much smaller role in the earlier drafts and did not even appear in costume, as the writers intended to put more focus on Spider-Man, and save Black Panther's origin for his own movie. However, when it looked like Marvel would not be getting permission to use Spider-Man, Black Panther's role was beefed up significantly. By the time they did get to use Spider-Man, T'Challa had already become so integral to the plot that they decided to leave his role as it was, and give Spider-Man a smaller part.
Alfre Woodard: (at around 17 mins) as Miriam Sharpe, the mother of an American citizen killed in the battle of Sokovia. Woodard was suggested for the role by Robert Downey Jr. before Marvel Studios learned of her casting as Mariah Dillard in Luke Cage (2016).
Jim Rash: (at around 16 mins) As the MIT liaison. The Russo brothers previously worked with Rash on Community (2009).
Stan Lee: Stan Lee's second cameo playing a delivery man. In this movie, he played a FedEx driver delivering a package to Tony Stark (Robert Downey Jr.). In Fantastic Four (2005), he played Willie Lumpkin, a USPS mailman who delivered Reed Richards's (Ioan Gruffudd) mail to him early in the movie.