Adaptation Displacement: Most people are more familiar with the movies than with their source material.
Alternative Character Interpretation: In the 1962 film, Rosie (the Love Interest) meets Marco on the train and they have a singularly bizarre conversation. (See an in-depth analysis of this scene, with a transcript of the crazy conversation, here.) Later she bails him out of jail and through a shorter but just as weird conversation we learn that she's left her fiancee for him despite only meeting him once. Then she has no impact on the rest of the movie at all other than to fill out some dresses very nicely. The very odd nature of Rosie and Marco's meeting and the general uselessness of her character has led some (including Roger Ebert; see his review here) to theorize that she's a Deep Cover Agent sent by the Chinese to keep an eye on Marco—although this raises the question of why Rosie did nothing to stop Marco as he unraveled the conspiracy around Raymond. Others guess that she's actually an American agent investigating the conspiracy, as Jonathan Demme did with the character in the 2004 remake. In the novel, Rosie's ex-fiancee (the one she returns a ring to so she can be with Marco) happens to work as a government agent, and he's the one who helps Marco investigate Raymond (the army, primarily Col. Milt, are the ones who fulfill this function in the 1962 film).
John Frankenheimer said on the DVD Commentary that the scene in question came straight from the book and he had no idea what that bizarre conversation meant.
Award Snub: It received two Academy Award nominations for Best Supporting Actress and Editing. It wasn't up for Best Picture, Director, Actor, Supporting Actor or Adapted Screenplay.
The conversation on the train is absolutely bizarre and never gets brought up again, and has been the source of fan theories for almost sixty years. See Alternative Character Interpretation above for more details.
From the remake, Marco's breakdown on the train is basically a triple play of these.
Contrary to popular belief, the titular Manchurian Candidate isn't the guy who gets brainwashed to perform an assassinationnote except in the case of the 2004 version, but rather a political candidate whose career will be assisted by the assassination. Nowadays, most people will refer to a "Manchurian candidate" as being someone who does anything that is asked of them, or as a catch-all term for Manchurian Agents in general.
A longstanding urban legend claims that Frank Sinatra bought the rights for the movie in order to bury it, feeling guilt over the movie's supposedly inspiring assassination of John F. Kennedy. This rumor appears to combine several facts: United Artistsdid block the movie from television screenings for a brief time out of respect for the late President,note It would not air on television until 1965 as a result Sinatra writing to ABC to complain about a television screening of his 1954 movie Suddenly, also about an assassination attempt, soon after Kennedy's death,note Suddenly is subject to a similar rumor that Sinatra tried to suppress the film after Kennedy's assassination. In reality, that movie simply entered the public domain after 1982 and fell into obscurity; Sinatra hardly needed to have suppressed a film few people remembered. and Sinatra obtained the rights in 1972, apparently to recoup money lost to the studio during a salary dispute. Sinatra, his daughters Nancy and Tina, and others denied that there was any attempt to "suppress" the movie, and Sinatra even claimed that he wasn't aware that he owned the rights to Candidate, implying that the deal was his agent's doing. Further, Candidate received several television screenings during the period it was supposedly "suppressed," though it wasn't until the rights reverted to MGM/UA in 1987 that the movie received a theatrical re-release, and afterward became widely available to the public.
Hilarious in Hindsight: In the book and original film, Senator Iselin took the number of communists in the State Department from a Heinz 57 sauce bottle. One of the inspirations for Eleanor Shaw in the 2004 remake was John Kerry's wife, Teresa Heinz Kerry, widow of Senator and Heinz heir John Heinz.
Jerkass Woobie: Raymond Shaw, especially in the 1962 film. Quite the Jerkass, but what happens to him is awful.
Memetic Mutation: "Raymond Shaw is the kindest, bravest, warmest, most wonderful human being I've ever known." It even got referenced in A Very Potter Musical.
Why don't you pass the time by playing a little solitaire?
The original film has flashbacks to Raymond and Jocie's prior relationship. The subplot itself is tragic and heartwarming but the montage of Raymond, Jocie, and the Senator laughing so uproariously so thoroughly saccharine.
Raymond's outfit at the costume party (a cowboy) makes him look like a child. To a lesser extent, Johnny looks like an idiot in his Lincoln costume.
A graphic depiction of a murder by asphyxiation with plastic wrap in the 2004 film. The victim gags and vomits while his eyes bulge and he claws desperately at his assailant, all to no avail.
Miguel Ferrer only gets about three scenes as Marco's superior Garrett, but his intense performance and implicit Heel–Face Turn are pretty memorable.
Protagonist Title Fallacy: In the novel and first film, the Manchurian Candidate is Senator John Iselin, a villain who is Mrs. Iselin's husband, confidante, and pawn. The 2004 film puts its own twist on this, referring to a corporation called Manchurian Global.
Politically Incorrect Villain: Mrs. John Iselin, big time. However, at least in the 1962 film, much of this is revealed to be a carefully constructed facade. For example, during her visit to Raymond's office, she is seen arrogantly bossing Chunjin around like a typical Karen, callously not even pretending to get his name right ("Chu Chin Chow - or whatever your name is - the steaks are to be broiled for exactly 11 minutes on each side, in a preheated grill, at 400 degrees. No more, no less."). However, in her final monologue to Raymond, she pronounces his name perfectly and makes it clear that they coordinated with each other closely on the assassination plot ("Chunjin will give you a two-piece sniper's rifle that fits nicely into a special bag").
So Okay, It's Average: The 2004 film is generally regarded as inferior to the original, but a good film in its own right.
Tear Jerker: Despite the saccharine montage earlier, watching as Raymond breaks down after the murder of Jocelyn and her father is heart wrenching. For the first time, Raymond has finally found a way to be happy. Then his mother ends it for him in the most horrific way imaginable.
Unintentional Uncanny Valley: The animated video used to brainwash the subjects in the 2004 film is just realistic enough to raise the hackles.
In the 1962 movie, the yellowface on Chunjin, and especially on archetypal Yellow Peril villain Dr. Yen Lo, would be much less likely to fly today. At one point Ben Marco even compares Yen Lo to Fu Manchu.
The story hasalsobeen accused of demonizing "masculinized" women and "feminized" men as a threat to the country.