Robert De Niro has said that despite having won an Oscar for The Godfather Part II (1974), he was still a relatively unfamiliar face, and was only recognized once while driving a New York cab during his research for this film.
Director Martin Scorsese claims that the most important shot in the movie is when Bickle is on the phone trying to get another date with Betsy. The camera moves to the side slowly and pans down the long, empty hallway next to Bickle, as if to suggest that the phone conversation is too painful and pathetic to bear; this shot also showcases his isolation and loneliness.
In the diner scene, 12-year-old Iris adds sugar to her toast which is already covered in jelly. Some viewers interpret this character trait as Iris still being a kid at heart; however, this was not the intention. The other hooker who walks the streets with Iris in the film was an actual prostitute whom Jodie Foster shadowed to prepare for her role. The prostitute (played by Garth Avery) was also a heroin addict and one way in which she would quell her addiction was to add extra sugar to her meals. Jodie, being a very young but very observant and intuitive young actress, incorporated this character trait into the scene.
Robert De Niro prepared for the role by working as a late night cab driver in New York City early 1975. One of his fares was a struggling actor who recognized him from The Godfather Part II (1974). The young actor said to De Niro discouragingly "Wait a minute, you just won an Oscar. My God... is it THAT hard to get work??"
Robert De Niro worked fifteen hour days for a month driving cabs as preparation for this role. He also studied mental illness, and during his off-time when filming 1900 (1976), visited a US Army base in Northern Italy and tape-recorded conversations with Midwestern soldiers so that he could pick up their accent.
Victor Argo: As shopkeeper Melio who is held at gunpoint by a robber (Nat Grant), who is shot by Travis Bickle (Robert De Niro), thereby saving Melio.
Martin Scorsese: Sitting down, behind Betsy as she walks into the Palantine campaign headquarters in slow-motion.