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.
Ariadne: Who would want to stay in a dream for ten years? Yusuf: Depends on the dream.
Alternative Character Interpretation: Are the main characters people we should be rooting for, or are they really Villain Protagonists? In a way it all hinges on whether Saito is sincere in feeling that Robert Fisher achieving total global energy dominance would be bad for the world, or if he's just using that as an excuse for wanting to weaken his competition in the market.
Are the main characters themselves Villain Protagonists simply out for a payday, or in Dom's case, a chance to reclaim a normal life.
Why isn't Ariadne considered wrong for invading Cobb's memories? He explicitly states that these are not dreams they are memories and then she runs down the hall into the elevator and goes straight to his most private memory.
Was Ariadne "wrong" in "invading" his memories, or was she trying to protect herself and the gang by informing herself of the dangers of Dom's mind and helping him confront his memories and move on? It's more complicated than mere secret-keeping.
Award Snub: Was nominated for Best Picture, Director, and Screenplay at the Golden Globes, but no nominations for acting (leading or supporting). It lost each of those to The Social Network (even Best Original Score.). At the Oscars, Nolan wasn't nominated for Best Director (yet still managed to nab Best Picture and Best Screenplay nods) while Lee Smith wasn't nominated for Best Editing.
It did win best sound editing, best sound mixing, best cinematography and best visual effects. The only other film to win as much was The King's Speech.
Common Knowledge: "Inception" or "[object]-ception" has now become the term for whenever one object is placed inside an identical object (or indeed any form of recursion), referencing the "dream within a dream" technique. "Inception" actually refers to planting an idea in the person's subconscious. The "dream within a dream" plan is just a method of performing the inception, and it's also used in the Bond Cold Open for an extraction job (which is the opposite of an inception job). Although this is an excellent example of how films have an effect on cultural terminology and vernacular.
One of these Earworms is actually derived from the other one. When you hear it, you'll shit bricks... It's implied that this music is in the movie because the characters are hearing it, distorted by the time dilation.
Harsher in Hindsight: Robert Fischer's father is dying of a long-term illness and passes away before the Inception begins. Just under seven months after the film was released, the actor (Pete Postlethwaite) lost his second battle with cancer.
The scene where Ariadne is in Cobb's dream, right after she presses the button leading to the proverbial Basement of Cobb's memories. The scene is presented in such a terrifying fashion; the elevator door opens and Ariadne steps into a fancy hotel room...that's been trashed. The background music is gone, and there's absolute silence. Then Ariadne steps on a glass. Then we see Mal. And she's looking at you. The net result of the entire scene can be summed up as Cobb has a grade-S Yandere in his subconscious and she wants out.
Ho Yay: Eames and "darling" Arthur, especially on Eames's part.
Especially when they're headed into the third level and Eames is getting all concerned about Arthur going up against security. It's amplified by the staging, since Arthur is kneeling by Eames's side and holding his hand. (To hook him up to the PASIV, but still.)
Even better in the French dub, where Arthur's answer ("I will lead them on a merry chase") is translated using the adverb gaiement ("gaily"). Yes, it carries the same connotation as in English, nope, it's not commonly used much anymore for that exact reason.
Solid example: while Eames is making his way through the hotel in the second dream, disguised as a gorgeous blonde woman, he stops Saito in the elevator and starts stroking his face. Saito looks pleasantly surprised at first, then catches their reflection in the mirrors, sees through the disguise, and realizes it's not a woman at all. Yeah... he wasn't so pleased then.
There's also a teensy bit of this between Cobb and Fischer during the bathroom scene.
And for the girls, Mal walking close to Ariadne and asking her if she knows what it's like to be a lover (which undoubtedly becomes even stronger in light of Ellen Page coming out in as a lesbian in real life). It Makes Sense in Context, but...
Launcher of a Thousand Ships: Arthur, if the kink meme page and fanfiction.net are to be believed. The usual suspects are (in descending order) Eames (Darlingshipping), Ariadne, Eames and Ariadne, and Cobb. Mal, Saito, and occasionally Robert Fischer too, though that's less common.
Magnificent Bastard: Saito. In the prequel comic, it's revealed that The Cobol Job was an attempt to get information from Saito's corporation, in an effort to keep Fischer's energy monopoly together. It appears that in actuality, this was all Saito's plan to lure Cobol's best and brightest to him, so he could audition them and steal them from under Cobol's noses, and use them to break up the very monopoly Cobol was trying to preserve.
Memetic Badass: Fandom has very rapidly turned Saito into one of these.
How about Eames's use of pet names being dialled Up to Eleven? In the film, he calls Arthur "Darling" once, with definite irony. But in many fanfics, he not only calls him "Darling" left, right and centre, but also "Love", "Pet" and sometimes "Sweetheart". And he often uses the same pet names for Ariadne (although she gets "Darling" less often because apparently that one belongs to Arthur) and occasionally other characters get pet names too. Sometimes it's almost like he's Spike without the bleached blond hair and vampirism. Unless it's a Vampire!AU fanfic, of course.
In the movie, the extractors have to be careful not to alert the projections to their presence or they will be physically assaulted, which Ariadne learns the hard way.
Outside of the movie, it's a similar problem that people had with The Matrix. What if, at this very second, you are asleep and there are people poking around in your brain searching for secrets? Or maybe you're stuck several layers down in your own dreams, and have forgotten. Maybe your entire "life" has taken place over a few minutes. Eek.
The biggest example is Dom demanding Ariadne tell him about the bypass in the snow base. He says there's no time, and demands that she tell him, but he doesn't even relay it to the team; he tells her to tell them. All he's doing is adding a step while she tells him, thus wasting time, and more importantly making sure that Mal knows the bypass as well.
Cobb refusing to shoot the evil projection of Mal before she temporarily kills Fischer, dragging him down into limbo, despite having known for years that she is just a projection, making his "How do you know that?" to Ariadne pointing this out to him making him look even more stupid.
And before that, Cobb actually expecting Mal's evil projection to stay in the chair he tied his rope to in the opening to keep it weighed down even though he should know not to trust her by that point.
Fischer Jr. The poor guy doesn't know a damn thing and got dragged into this dreamy mess just because a Japanese businessman wants him to split his company. He got a daddy issue in the real world and then Cobb's team hijacked his mind, injected a (probably) false solution to his daddy issue and made him believe what Saito wants him to believe. Plus, what with the seed of doubt the team planted in him, he will most likely come to distrust his godfather from now on — the only family he has left.
Cobb as well. Living with the guilt and belief that he caused his wife's death, being on the run for being falsely accused of murdering her (though not too far from the truth), probably never getting to see his kids again, and always being tormented by visions of Mal in long-held dreams really makes you want to hug the poor guy.
Mal (the living one) as well. She killed herself fully convinced that this would cause her to wake up in the real world, so she could be with her real children again, unaware that this was the real world maybe, and those were her children. And it all happened because her husband underestimated the power of the suggestion he implanted in her mind. Her dream-self, however, is a...
Jerkass Woobie: Yes, she ruined Cobb's life by framing him for her suicide, but this was only because she had spent so much time in the dream world that she was unable to distinguish what was a dream and what was reality. This would lead to her killing herself, convinced that she could wake up into what she perceived as reality. In the end, all she wanted was to go someplace where she could be happy forever. Of course, it turns out that her delusion and paranoia is a direct result of Cobb implanting the idea of it in her mind.