* AwesomeDearBoy: As the premise of the film was kept secret, Creator/LizzyCaplan signed on simply because she was a huge fan of ''{{Series/Lost}}'' (which Creator/JJAbrams produced) despite [[ActingInTheDark knowing nothing else about it]].
* CaliforniaDoubling: Although majority of scenes were filmed on location in New York, several places were doubled by California. The exteriors at the electronics store were filmed in downtown Los Angeles, and the Bloomingdale's in the movie was actually in Arcadia.
* ChristmasRushed: It had to be rushed into production (which started in August 2007) to be ready in time for its stone-set date of January 18th, 2008 (the trailer, which was released a month earlier, came out while the film was still in pre-production).
* CreatorInJoke: Jason can be seen wearing a 'Slusho!' t-shirt - a brand of drink from ''{{Series/Alias}}''. It also played a considerable role in the ARG.
* DarkHorseCasting: As became the norm with 2000s found footage films, unknown actors were cast in most of the major roles to allow the audience to feel as though they were watching this happen to real people. Interestingly enough, the two more recognisable actors, Mike Vogel (for ''Film/TheSisterhoodOfTheTravelingPants'' and ''Film/RumorHasIt'') and Lizzy Caplan (for ''Film/MeanGirls'') are [[spoiler: the first ones killed off]]. TJ Miller made his film debut as Hud.
* ExecutiveMeddling: Averted, [[ZigZaggedTrope and not.]] The relatively low budget of the film allowed the filmmakers to keep the nondescript title and DownerEnding (see above) despite concerns from Paramount, but executives maintained that the film be PG-13 instead of the R rating the creators wanted. When the filmmakers planned a single use of the word "fuck" (as allowed in a PG-13 film) an ExecutiveVeto was made against it, on the grounds that the MPAA descriptor warning about even a little coarse language would stop some parents from the mid-western U.S. from bringing their kids (why they thought anyone [[WhatDoYouMeanItsNotForKids would want to bring]] ''[[WhatDoYouMeanItsNotForKids kids]]'' [[WhatDoYouMeanItsNotForKids to this movie]] is anyone's guess).
* FakeAmerican: Jessica Lucas (Lily) is Canadian. Of course there's no reason the character couldn't be a Canadian living in New York either.
* LyingCreator: Actually, the ARG generally answers very little about the movie, but replaces general questions with more in-depth ones.
* ShownTheirWork: Without credits, the film runs at 80 minutes. That is the length of a long-running Mini DV tape, which was a common format used in consumer camcorders.
* ShrugOfGod: The creators have left it intentionally ambiguous as to whether or not [[spoiler:Lily was successfully evacuated and survived]].
* ThrowItIn: Upon seeing a cut of the movie, Steven Spielberg suggested giving the audience a hint at the monster's fate during the climax. They added in a [[spoiler: countdown overheard on the helicopter's radio, and the sounding of air raid sirens to signal the Hammer Down bombing.]]
* ViralMarketing: The film was one of the first to actively use viral Internet marketing as a major draw; there's a reason it was dubbed "''Film/TheBlairWitchProject'' for the [=MySpace=] generation." The very first website was simply "1-18-08.com." It contained various strange photos, including frightened-looking people, a Japanese chef cooking a seafood dish, a ruined oil rig, and--most terrifyingly of all--pictures of ''humpback whales'' with massive bites taken out of their bodies, suggesting that the monster was large enough to devour some of the biggest creatures on the planet. As the months between the trailer and the film passed, more sites were discovered, with people endlessly dissecting every possible clue. Among the other sites:
** [[http://www.slusho.jp/ The Slusho website]], a masterpiece of deliberate BlindIdiotTranslation.
** [=MySpace=] pages were set up for the characters, and the last date anyone logged in was the movie's release date.
** The homepage of the mysterious Tagruato Corporation, which would later revealed to be responsible for the deep-sea drilling that awoke Clover in the first place, and this tied into their subsidiary, Slusho!. Apparently, Slusho is made with a special ingredient, eventually translated from Japanese into "seabed's nectar", that they found deep in the ocean, see...
** T.I.D.O.Wave, a radical environmental group that protested Tagruato's actions. Notably, the Tagruato homepage was defaced by their "agents," and fans had to decipher a code to find who was responsible.
** A young woman whose boyfriend worked with T.I.D.O.Wave created a series of vlogs documenting her relationship and search for him after he disappeared. In the movie itself, she shows up for a few seconds, passed out on a couch in Rob's party - the last vlog is set right before the movie's events, and indicates the reason she's passed out is because she ate a substance her boyfriend smuggled to her ([[IdiotBall and specifically told her not to eat]]) from his stint doing undercover work at Tagruato. That subtance was Slusho's seabed nectar in its raw form; all we know years later is that it has a drug-like impact on consumers, and that Clover's parasites have high levels of it in their blood. Considering what happens to Marlena, it's possible the FDA should've looked over Slusho a bit more closely.
** After the DVD was released, a final website emerged that was password-protected; fans had to use a code on the DVD's box to unlock the site and get a few new photos of Tagruato's deep-sea exploration and its consequences.
* WhatCouldHaveBeen:
** A lot of scenes and aspects concerning the monster had to be cut in the final version or left out. One such scene showed the monster using some sort of "feeding tube" to violently devour fleeing people in what probably would have been the most horrific scene in the movie.
** [[spoiler: One of the alternate endings included on the DVD hint that Rob and Beth (or at least Beth) survived the Hammerdown bombing.]]
** ''Greyshot'' was a proposed title to the film, named after the grey lines that show up when reel video is paused and the Greyshot Arch that the surviving characters hide under at the end of the film.
** The monster was supposed to destroy the bridge with one of his hands, but filmmakers found that too deliberate. They changed it to the tail, to make it seem more accidental.
** Scenes with the parasites were shot with puppets originally, but the subway scene in particular turned out to be more interactive - so CGI was used instead. The puppets were also thought to be too goofy looking.
** [[spoiler: Hud lived]] in the original draft. They opted to [[spoiler: have him eaten by the monster]], and it was supposed to be instant at first too. It was changed to be longer to [[spoiler: give the audience a good look at the monster]].
** Creator/JohnKrasinski reportedly considered having ''Film/AQuietPlace'' be part of the Cloverfield expanded universe at one point, but instead opted to make it a standalone film instead.
* WorkingTitle: The aforementioned ''Greyshot'', ''Clover'', and ''Monstrous'' were all early titles. ''Cheese'', ''Chocolate Outrage'', ''1-18-08'', and ''Slusho'' were all fake working titles to throw off the fans.
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