Anthony Mackie's appearance in this film fulfills his dream of playing a Marvel comic book character. He wrote a series of e-mail pleas to Marvel, wanting to play any comic character that would appear on film. Though the studio repeatedly replied to him that they will respond in due time, Mackie's emails caught the attention of producer Kevin Feige, who subsequently offered him the role of Sam Wilson a.k.a. Falcon.
Unlike other films in the Marvel Cinematic Universe, this movie minimized the use of visual effects as much as possible. Anthony Mackie elaborated: "The Russos, what they did that was so great was, they wanted to stay with live-action, which is a dying art form. If they could build it, they built it. If we could do it, we did it. They wanted to do as little CGI as possible. That's why the movie looks so great."
Robert Redford wanted to do the film because his grandchildren are fans of Marvel films, and he wanted them to see him in one.
When asked why Tony Stark, Bruce Banner, or any of the other Avengers weren't called to help Captain America or Black Widow in the film, the screenwriters explained that the movie only takes place in about three days, therefore the characters didn't have a chance to contact them.
Christopher Markus, Stephen McFeely: The film's writers appear as the two S.H.I.E.L.D. interrogators.
Danny Pudi: (at around 1h 35 mins) As the Com Tech operator who lets Captain America into the communications room. The Russo brothers previously worked with Pudi on Community (2009).
Steven Culp: (at around 2h) The Representative who angrily interrogates Black Widow at the hearing is better known for playing the antagonistic Speaker of the House in The West Wing (1999) and CIA Agent Clayton Webb on JAG.
D.C. Pierson: (at around 55 mins) The big bearded man in the Apple Store at the mall with Natasha and Steve hiding in plain sight while Brock's team pursuing them.