These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Award Snub: Although the film took home a much-deserved Oscar win for Cinematography (as well as nominations for Director and Editing), neither Orson Welles' performance nor the iconic zither score were nominated.
Complete Monster: Harry Lime steals penicillin from hospitals in post-World War II Vienna, waters it down to the point of uselessness in order to make it go farther, and sells it back to the open market. It's saying something when the lucky ones are those who merely die from the now-lethal medicine: many people, including children, go insane and die painfully. All this happens and Lime doesn't even feel any remorse.
Magnum Opus: Easily Carol Reed's most recognizable film. However, slightly subverted. Due to how heavily Orson Welles' performance has played into the film's legacy, some mistakenly believe that he directed it instead.
Moral Event Horizon: Lime faked his death to avoid being accused of selling watered-down penicillin that resulted in mass death and illness.
Older Than They Think: Only not that much older. The "cuckoo clock" speech quoted at the top is the most famous line from the movie. What most people don't realize (even though it's lampshaded) is that Harry Lime is actually quoting someone. "As the fella says..." Who's the "fella"? Winston Churchill. (Yeah, not one of Churchill's more inspiring quotes.)
One-Scene Wonder: Orson Welles appears less than 10 minutes on screen; nonetheless, he is the most remembered part of it. Welles was conscious of it, he told Peter Bogdanovich that it was an old theatre convention, citing "Mr. Wu" where most of the plot revolves around describing Mr. Wu and then Mr. Wu makes a grand entry and the audience says, "Mr. Wu gives a great performance!".
The Woobie: Anna Schmidt is so sad and pathetic that even the sad and pathetic Holly Martins can't stop himself from falling in love with her. It's noteworthy that her theme is the only piece of music in the movie that ISN'T Soundtrack Dissonance. It's full on SAD.