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."
(at around 15 mins) Nick Fury relates a story of his grandfather being an elevator operator. In real life, Samuel L. Jackson's grandfather was an elevator operator.
Robert Redford wanted to do the film because his grandchildren are fans of Marvel films, and he wanted them to see him in one.
Sebastian Stan is contracted for nine films, but according to him, when production for this film began, he was not told anything of which films he will be incorporated. Stan only realized he was playing the title role of the Winter Soldier when the title was formally revealed in San Diego Comic-Con 2013.
Ed Brubaker: (at around 1h 27 mins) A scientist at the birth of the Winter Soldier is played by the author of the Winter Soldier comic book.
Gary Sinise: (at around 18 mins) The info voice narrating the history of the Howling Commandos in the museum.
Joss Whedon: (at around 18 mins) Writer and director of Avengers (2012) and Avengers : L'Ère d'Ultron (2015) as the man wearing a Captain America t-shirt, and going down the escalator with a little boy at the Smithsonian Institution.
Stan Lee: (at around 1h 30 mins) As a security guard at the Smithsonian Institution, who notices the original Captain America costume is missing and says "I am so fired."
Christopher Markus, Stephen McFeely: The film's writers appear as the two S.H.I.E.L.D. interrogators.
Joe Russo: as Dr. Fine, a surgeon who works for S.H.I.E.L.D. and performs emergency surgery on Nick Fury.