In addition to So My Kids Can Watch (see below), Robert Redford wanted to be in this movie so that he could play a villain, since he almost never gets cast as one. Another reason he's mentioned is that he's never been in such a special effects-heavy movie before.
California Doubling: Cleveland doubles for Washington, D.C. You see a lot of Cleveland landmarks during the police chase that Fury is lured into early in the movie (even a directional sign for US 6 appears). Furthermore, there are a lot of tall skyscrapers seen during the police chase and in other parts of the movie. You will never find such buildings in real Washington, D.C. because the Height of Buildings Act of 1910 prevents any building in D.C. from being more than 20 feet taller than the width of the street that said building sits on (the Washington Monument is in fact the tallest man-made structure in the city). The buildings seen in the chases are much too tall for this city to actually be Washington, D.C.
Cast the Expert: Batroc's moves are pretty convincing — and that's probably because his actor Georges St-Pierre is one of the pound-for-pound greats of MMA: a long-term welterweight champion of the UFC with nine title defenses.
One of the first revealed deleted scenes was a short, painful conversation between Natasha and Fury about his decision not to bring her in on his survival plan. Scarlett Johansson suggested it be cut because it disrupted the momentum of the film, and the basic gist of the scene is still conveyed without being needed to spell it out. Albeit, this scene also introduced the photo-veil, the high tech mask that allow Natasha to impersonate the female councilwoman and enter the Triskelion.
One scene reveals a pragmatic reason why Steve ditches the S.H.I.E.L.D. version of the Captain America uniform, even for the final confrontation (putting aside the symbolic reasons for using the WWII outfit). After he escapes the assassination attempt in the Triskelion, HYDRA is able to track his location through a tracker installed in the suit. However, Steve appeared to know about it, and leaves it behind at a public gym for a set of sweats. The STRIKE team comes across it stuffed in someone's duffel bag.
Another deleted scene was one of Maria Hill and Sitwell conversing after Cap's escape, ending with her being put under investigation because of her mild taunt that Rogers tends to inspire loyalty.
The dialogue between Pierce and Natasha about potentially leaking her past alongside the entire S.H.I.E.L.D. database ran longer, with a mention that Pierce isn't doing anything to stop it because HYDRA's existence being known to the public won't matter once the Helicarriers are fully operational.
A deleted scene that wasn't filmed was one of Hawkeye being sent to hunt down Steve, catching up to him and the two of them fighting. Steve wins, but finds Hawkeye whispering to him to make his defeat look real, revealing Hawkeye deliberately lost because a Quinjet is recording the whole thing overhead. He also alerts Steve about the tracking device in his suit.
Another unfilmed scene was one taking place after the reveal of HYDRA and computerized Zola. In it Zola would have explicitly been shown to survive by transferring his mind to a robot body, which promptly flees before Pierce's missile strike. It was cut out because the Russos felt uncertain about leaving such a major loose end hanging by the end of the film; however, the finished scene is ambiguous enough that Zola could indeed return if they wanted to.
Besides playing a villain, Robert Redford reportedly wanted to experience the new style of film-making that utilised high technology to bring its characters to life.
During the highway battle between the Winter Soldier and Cap, the villain does a knife flip to try and catch Steve by surprise. Reportedly, during all the days before the scene was shot, Sebastian Stan was seen flipping a toy knife until he could perform the action effortlessly.
Fake American: Inverted. Councilman Singh is Indian. His actor Bernard White is Sri Lankan-American.
Robert Redford joining a superhero film is not the kind of thing one would generally expect from him. He also uncharacteristically plays the villain of the film. Heck, the directors have commented that, in an earlier age, the idea of Redford playing Captain America himself would not have been all that far-fetched. The directors' commentary notes that the style of the movie was inspired by '70s political thrillers, even referring to Three Days of the Condor, in which Redford was the protagonist. In a way, The Winter Soldier is Redford redoing the movie as the guy running a conspiracy instead of the agent being hunted, making this also an example of Playing with Character Type.
Production Posse: Danny Pudi, who stars in the Russo brothers-directed Community, cameos as a S.H.I.E.L.D. technician. The firm who did all the openings for the Russos' shows was responsible for the end credits. Alison Brie was also in the mix to play Agent 13.
Promoted Fanboy: Anthony Mackie is a huge fan of the Falcon, and has gushed multiple times about how lucky he's been to get the role. He even expressed disappointment that his costume wasn't the character's classic red and white spandex. It's also heartwarming that one of the things he was emphatic about when joining the project was that he was playing Marvel's first African-American superhero.
Reality Subtext: Chris Evans and Scarlett Johansson have worked on three other movies together and their natural friendly chemistry and close working relationship applies very neatly to Cap and Widow. Likewise, Evans and Anthony Mackie were both in two movies previously, but never worked together. According to Evans, they later ran into each other at the library, struck up a conversation, and just clicked as friends, which probably lends a little verisimilitude to Steve's and Sam's first meeting, too.
Audiences get their first look at Aaron Taylor-Johnson and Elizabeth Olsen as the MCU's Quicksilver and Scarlet Witch; they're the co-leads as husband and wife in Godzilla (2014), opening one month after Cap.
Joe Russo: What it was going to be, we were trying to complicate the relationship between Cap and his S.H.I.E.L.D agent friends. If Hawkeye got a call from S.H.I.E.L.D saying Captain America is a fugitive, would he listen to that call or not listen to that call? That sequence actually was heartbreaking for us to cut it. I think it ultimately might have been a conflict with Renner's schedule. But there was a great sequence where Hawkeye was chasing Cap through Washington D.C. there was an awesome sequence where they confronted each other in a ravine on the outskirts of D.C. and Hawkeye was shooting a series of arrows closing in on Cap, Cap closing in on him. And then Cap took him down and he realized for the first time that Hawkeye was trying to trick S.H.I.E.L.D, where he whispered something into Capís ear that Cap had a tracker on his suit and to punch Hawkeye to make it look real, because there was a Quinjet hovering above where they were watching the feedback back at S.H.I.E.L.D.
Originally the opening to the film was going to be a wartime flashback of Steve Rogers fighting alongside Bucky and the Howling Commandos, ending with a reveal that it was All Just a Dream, and Steve looking at a newspaper reporting of Dum Dum Dugan's recent death. It can be seen here. This introduction would have presumably taken the place of the visit to the Smithsonian and the "End of the line" flashback scene.
Baron von Strucker was going to be the Big Bad of the film, rather than Alexander Pierce. Clay Quartermain was also planned to appear, possibly taking Sitwell's place.
For the scene where Jenny Agutter's character takes out a room full of mooks before revealing herself to be Black Widow in a Latex Perfection mask, they were going do the fighting with a stunt double. Agutter lobbied to do it herself, citing her ballet training.