* AlternateCharacterInterpretation: The aliens. Their complete lack of armor and weapons is usually cited simply as an example of WhatAnIdiot, but some more serious hypotheses have been put forward. The two most prominent are that they aliens were actually peaceful, and only began attacking humans after the humans were aggressive towards them, and that they were actually demons defeated by holy water.
** An alternate take is that we're not supposed to understand why. The movie is attempting to convey an alien invasion not from a gutsy action hero's perspective who blows stuff up and saves the day, but from a normal family who's just trying to hunker down and live through it. We don't understand why the aliens do what they do the way they do because said family almost certainly wouldn't have any clue.
** In-Universe, the radio personality speculates near the end of the film that the aliens were only committing a massive raid and not trying to invade or conquer the planet, citing that he saw them drag a man and his family into their ship as evidence.
** A less serious interpretation is that this was the aliens' version of a frathouse prank, akin to forcing a pledge to try to, say, get honey from a beehive naked or something.
** They could also be a race similar to Creator/StephenKing's ''Literature/TheTommyknockers'', who use all manner of advanced technology but don't actually understand any of it and are actually fairly stupid.
** Another interpretation, this one explored somewhat by ChrisStuckmann in his examination of the film, utilizes some fridge logic. Why would a race of aliens with a weakness to water travel to what, from their perspective, is essentially a DeathWorld? They're not stupid, they're just incredibly desperate for resources.
* BigLippedAlligatorMoment: The scene in which Graham and the kids come across an illustration in Morgan's book that shows a house that looks just like theirs set on fire, with three people (a man and two kids) lying dead outside it. The scene is pretty lengthy, is filled with ominous music and set-up, and yet it's never explained or brought up again.
* CriticalDissonance: Upon release ''Signs'' was regarded by critics as being a pretty good film by M. Night that still proved his talent for building suspense. Among casual filmgoers, though, it's grown to become a laughingstock of inept horror akin to ''Film/TheWickerMan'' remake or M. Night's later film, ''Film/TheHappening''.
* CriticalResearchFailure: Despite Shyamalan being from Philadelphia, his version of Bucks County is hilariously wrong... to the point that Bucks residents didn't even ''realize'' it was set in their county initially, let alone the ''county seat.''
** The uniforms the police wear don't look anything like what any officers in Bucks County wear or have ever worn - Sheriffs, deputies, state patrolmen, local police, or anything.
*** To wit: Officers in Bucks all wear blue uniforms, not brown. The jackets they wear are blue windbreakers, not brown with fur trim. They also don't wear wide-brimmed hats; they wear standard police hats, if any hats at all (most don't). Ultimately, the police uniforms seen in the movie look like California outfits, rather than Pennsylvania uniforms.
** There are no large farms at all within the vicinity of Doylestown, as the entire area is much too hilly for proper farming, and by now much too developed.
** There are also no large natural bodies of water within ''miles'' of Doylestown - where that lake came from is anyone's guess.
** While there ''are'' a ludicrous number of trees in Bucks County and Doylestown especially, which give a little privacy, it's also so densely populated that it's literally impossible for a farm to be secluded - there would have been at ''least'' two dozen houses within short walking distance and probably ''line of sight'' of the farmhouse.
** The setting as a whole looks nothing like Bucks County except maybe the northern-most areas; it actually bears more of a striking resemblance to the Poconos about a half-hour farther north.
* CrowningMusicOfAwesome: James Newton Howard's score. PERIOD. "Hand of Fate" in particular.
* FridgeLogic: How exactly would the aliens have dealt with something like, oh, a rainstorm? Or snowpack in the parts of the world that were experiencing winter at the time? This may be the only alien invasion at risk of getting called off on account of weather.
* HellIsThatNoise: That clicking, almost-but-not-quite normal sound coming from the baby monitor? It's the aliens.
* HilariousInHindsight: The scene where Graham finds it hard to cuss and scare intruders off his farm was already funny in the first place. Post Mel Gibson's widely publicized, coarsely worded fits? ''Hysterical''!
* IdiotPlot: As mentioned... everywhere, the aliens invading a planet that's covered in 70% water without wearing so much as ''shoes'' when water is completely toxic to them, don't have weapons, and are easily captured, outwitted, or outsmarted by random people.
* ItWasHisSled: Even those who have not seen the movie are often aware of the twist. Shyamalan movies in general are vulnerable to this.
* MemeticMutation: The [[NightmareFuel disturbing]] "It's Behind" scene is probably the most parodied in the movie, due to its over-the-top drama and suspense leading up to the alien's appearance. It was mostly parodied on {{YTMND}}, though.
* MoralEventHorizon: The alien that stays behind does so because he wants revenge on Graham for cutting off his fingers. All right, that's understandable...wait, he's going to get revenge on Graham by attacking, with murderous intent, ''Graham's son?'' Dick move.
** It is stated by Merrill that the aliens left their wounded behind so the alien at the end most likely didn't stay of its own accord.
* {{Narm}}: The movie would actually be a pretty good thriller if it wasn't for the mind-numbingly stupid decision to have the aliens be weak to ''water''. Also, Bo's bizarre behavior fluctuates pretty wildly between being genuinely unsettling and so over-the-top it's goofy.
* NarmCharm: Despite the NightmareRetardant noted below, the film ''does'' manage to be pretty scary and powerful for the most part. It helps that the aliens spend most of the movie [[NothingIsScarier off-screen]].
* NightmareRetardant: One of the more infamous cases. The direction surrounding the aliens is genuinely creepy, but by the end of the movie, you realize that you were cowering in fear of a monster that's barely stronger than a normal human and would treat a garden hose like a flamethrower.
* OlderThanTheyThink: The death of Graham's wife is taken beat for beat from an old {{Glurge}} story circulated on the internet.
* RetroactiveRecognition: [[Film/{{Zombieland}} Little Rock]] saves the world, by being really, uh, [[GainaxEnding OCD]]?
* WhatAnIdiot: The aliens, as explained under FridgeLogic. What were aliens vulnerable to water thinking in invading Earth?
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