* ActorAllusion:
** Creator/NathanFillion appears in ''VideoGame/{{Halo 3}}'', voicing [=GySgt=] [[{{Series/Firefly}} Reynolds]]. He also appears in ''VideoGame/Halo3ODST'', as a sergeant leading a squad that includes characters portrayed by Creator/AdamBaldwin and Creator/AlanTudyk. [[Series/{{Firefly}} Again!]]
** In [=H3=], Creator/AdamBaldwin voices an ODST who yells: [[{{Series/Firefly}} Gee it sure would be nice if we had grenades, don'tcha think?]]. In ''ODST'', his character yells out "Gorramit!" occasionally, another ''Firefly'' reference.
** Creator/KateeSackhoff, the actress who portrays Kara Thrace in the 2003 revival of ''Series/{{Battlestar Galactica|2003}}'', voiced a marine in ''Halo 3''. You can hear her yelling "Frak!" if she gets hit.
* AdoredByTheNetwork: It's becoming clear that Microsoft loves their franchise based on references cropping up in their other products. Besides the smartphone assistant named after Cortana, the replacement for Internet Explorer, Microsoft Edge, was codenamed Spartan while the Windows 10 codename was Threshold, the name of the fictional gas giant that Alpha Halo orbits.
* AscendedFanon: The first edition of the ''Halo Encyclopedia'' pretty clearly copied a lot of its information from the ''Halo'' wiki, including several of the latter's errors. While Creator/ThreeFourThreeIndustries have said that the ''Encylopedia''[='s=] errors should not be considered canonical, one bit of fanon that snuck ''has'' managed to become official canon; the United Rebel Front, which originated from a misinterpretation of a single line in ''Literature/HaloGhostsOfOnyx'', was eventually established as an official faction in later ''Halo'' media.
* CashCowFranchise: Ten games,[[note]]Counting ''ODST'' and the ''Wars'' duology but not the low budget twin-stick shooters.[[/note]] various books and comics, the requisite action figures, an ''anime series'', two mobile games, several {{Alternate Reality Game}}s, and two live-action serials, not to mention various promotional tie-ins. As of 2015 [[https://www.bloomberg.com/features/2015-halo-5-bonnie-ross/ the franchise had sold 65 million games grossing $3.45 billion in revenue]], plus another $1.2 billion from non-game media, making it one of the biggest sci fi franchises of all time. By 2021 the games have sold 81 million copies.
* CastTheExpert: Pete Stacker, who voiced Captain Jacob Keyes and Sergeant Stacker, was a Vietnam veteran. An outtake on the Bungie website has him talking about [[https://halo.bungie.net/images/games/halo/audio/outtakes/stacker/incoming_vs_outgoing.mp3 hearing incoming artillery fire for the first time]].
* CreatorBacklash: Bungie began to regret what it created; note that this only applies to the ''franchise'' specifically. They're proud of their own games, but were neutral-to-hostile when it came to the spin-off games, novels, etc. that cropped up around them, despite originally giving their blessing. According to Eric Nylund, author of several of the EU ''Halo'' novels, [[http://ericnylund.com/?p=1256 Bungie tried to kill the whole EU project in the cradle halfway through the first novel]], thinking that the EU filled in too many details that would be [[RuleOfPerception best left to the players to decide for themselves]], most notably [[VanillaProtagonist Master Chief's personality, which they wanted to be a blank slate]] a la previous FPS protagonists. According to Ensemble Studios founder Tony Goodman, Bungie flat-out said that letting spin-offs be made (like the ''Halo Wars'' project he worked on) constituted [[https://www.gamesindustry.biz/articles/2012-09-27-halo-wars-bungie-saw-it-as-whoring-out-franchise-says-ensemble-founder "whoring out the franchise."]] This may be the reason that ''VideoGame/HaloReach'' [[ArmedWithCanon crapped all over the meticulously-laid timeline of the extended universe]].
* CreatorDrivenSuccessor: The series is made by Bungie, who also created the ''VideoGame/{{Marathon}}'' games. ''WebAnimation/RedVsBlue'' references this now and again.
** To elaborate, the original Halo CE could just as well have been called "Marathon 4", due to the abundance of elements (technology, terminology, texture and weapon design, etc) lifted wholesale from the Marathon games and the game itself fitting neatly into the segment titled "This century intentionally left blank" in the official timeline of the Marathon setting. Subsequent installments reduced the connection between the two, the most important change being the clear delineation that the Forerunners are not related to the Jjarro in any way due to conflicting timelines.
** There are also several multiplayer ones. For example, Guardian is a spiritual successor to the Halo 2-era Lockout, Sword Base is a spiritual successor to both Prisoner and Boarding Action, etc.
* CreatorKiller: Even by tabletop game standards, ''Fleet Battles'' and ''Ground Command'' sold absolutely ''horribly'' and were the direct reason the once-promising Spartan Games ended up closing their doors in 2017.
* TheDanza: Recurring marine sergeant Marcus P. Stacker is voiced by Pete Stacker[[note]][[DontExplainTheJoke The "P" stands for "Peter"]][[/note]].
* {{Defictionalization}}: The Windows Phone and Windows 10 digital assistant [[http://www.theverge.com/2014/4/2/5570866/cortana-windows-phone-8-1-digital-assistant is named Cortana.]] Creator/JenTaylor even voices her, [[StealthPun and the avatar is a halo]]. WordOfGod states that the two are completely different entities, though she does give some {{Continuity Nod}}s [[https://www.youtube.com/watch?v=YFweSyEQiv0 if you ask the right questions.]]
-->'''Question:''' Which is better, you or Siri?
-->'''Answer:''' Not to brag, but apparently I'm going to save the universe in about 500 years.
* FakeAmerican: [=SgtMaj=]. Avery Johnson was voiced by the British Creator/DavidScully.
* FranchiseZombie: Originally, the franchise was supposed to end in ''2''. Then it was supposed to end in ''3''. Now it has seven games in the FPS genre ''alone'', with more scheduled to come, though the original studio that created the franchise doesn't even own it anymore.
* GodNeverSaidThat:
** Before ''VideoGame/HaloWars'', ''Halo'' fanon had claimed that the armor worn by Arbiters was the same exact suit that it had been through history, the successor receiving it after his predecessor had died (which is implied, but not said, in ''Halo 2'', with the Prophets saying that the bodies were all in the mausoleum, and the armor's systems being outdated). However, the Arbiter of ''Halo Wars'' [[BloodKnight Ripa 'Moramee]] was killed and pushed down a chasm before his body was destroyed in a EarthShatteringKaboom. Henceforth, that meant the armor had been destroyed with it. Fans were annoyed, but it was later pointed out that since the Arbiter is intended to be sent on suicide missions, there would have been many cases where the armor was destroyed and/or impossible to recover. Such as falling to the core of a gas giant, like Thel 'Vadamee was about to.
** One of the major complaints from the fandom when 343i took hold is that they made the Jossed the idea that the Forerunners were human, and instead established the ancient humans as another species entirely. Many fans seemed to think the Bungie-Era games unambiguously painted the Forerunners as ancient humans, and that 343i was retconning a major aspect of the franchise. In reality, there was always enough evidence (both in the Bungie games and in the EU) for both interpretations of the Forerunners, so what 343i did was more like CuttingOffTheBranches on a MultipleChoicePast than anything else.
* HireTheCritic: [[http://en.wikipedia.org/wiki/Luke_Smith_(writer) Luke Smith]] of 1UP got hired to {{Creator/Bungie}} after he wrote the article "[[http://www.1up.com/features/broken-halo Broken Halo]]", where he criticized ''VideoGame/{{Halo 2}}'s'' multiplayer for being highly unbalanced. Following that, he put some real work into designing the multiplayer for ''VideoGame/{{Halo 3}}'' and ''VideoGame/HaloReach''.
* LongRunners: 20 years and counting. Since 2001 the franchise has seen seven main games (''Combat Evolved'', ''2'', ''3'', ''Reach'', ''4'', ''5'', and ''Infinite''), one standalone expansion pack (''3: ODST''), two RTS games (''Wars'' and ''Wars 2''), and a canon series of DLC missions for ''4'' (''Spartan Ops''). Plus dozens of pieces of spin-off media including novels, mobile games, comic miniseries, animated movies, live action web series, tabletop games, and even in-universe encyclopedias and [[ShowWithinAShow books.]]
* MidDevelopmentGenreShift: The first game was originally conceived as a RealTimeStrategy game, but it made it to shelves as a FirstPersonShooter, probably because its plot and factions coupled with its genre would have made it too similar to RTS heavyweight ''VideoGame/{{Starcraft}}''. [[VideoGame/HaloWars They eventually revisited the RTS idea, though]].
* NewbieBoom: Pre-''Halo'', {{Creator/Bungie}} had a small but very dedicated fan community, primarily drawn from previous Bungie titles like ''VideoGame/{{Marathon}}'' and ''VideoGame/{{Myth}}'', with whom they kept a very close relationship, hosting fan events, or attending events organized by fans. They even would release a few teasers into the fan community before any formal announcements had been made (such as with "[[http://marathon.bungie.org/story/cortana.html The Cortana Letters]]".) When ''Halo'' came onto the scene, the fan community experienced an explosion in population size, often completely bypassing the original "old school" community entirely and forming vast new communities which quickly overshadowed them in size and visability. The older Bungie community is still alive and active, but is now a small piece of a much larger whole.
* TheOtherDarrin:
** Both Miranda Keyes and the Prophet of Truth got new voice actors in between ''Halo 2'' and ''3''.
*** Truth's voice changed from [[Film/TheCrow1994 Top Dollar]] (Creator/MichaelWincott) to [[{{Film/Superman II}} Zod]] (Creator/TerenceStamp).
*** Keyes changed from Creator/JulieBenz to Justis Bolding. Additionally, the character got a new (and sexier) design as well.
** In ''Anime/HaloLegends'', John-117 is voiced by Creator/DavidWald instead of Steve Downes, while Cortana is voiced by Creator/ShelleyCaleneBlack instead of Jen Taylor. Additionally, neither of them apparently voiced the ''{{VideoGame/Halo 4}}'' teaser trailer, though they both came back for the game proper (which was the first time they actually worked side-by-side[[note]]they had never even met until '''2010'''[[/note]]).
** Avery Johnson was voiced by an uncredited actor in ''VideoGame/HaloWars2'', as David Scully was involved with a [[https://en.wikipedia.org/wiki/2016-17_video_game_voice_actor_strike video-game voice-actor strike]] at the time.
* ReferencedBy: In ''VideoGame/{{Stellaris}}'', one [[BigDumbObject Megastructure]] you can build is a RingWorldPlanet. Doing so may net you a visit from a neighbor civilization concerned that it might be a WeaponOfMassDestruction.
* ScrewedByTheLawyers: ''The Master Chief Collection'' originally introduced skins for the Warthog in ''Halo: Combat Evolved'' inspired by the paint jobs of the jeeps in ''Film/JurassicPark'', complete with descriptions using quotes from the film. These were later removed and replaced with new skins, presumably due to this trope.
* WhatCouldHaveBeen:
** Among the most famous, [[TropeCodifier influential]] and [[CashCowFranchise profitable]] console first-person shooters ever... was originally going to be an {{RTS}}. For '''Mac'''.[[note]]Except not really, Halo was originally being developed for Microsoft Windows, a first for Bungie, when they were invited to MacWorld 1999 they had to scramble to put together a Mac port. Steve Jobs just falsely claimed it was being developed for Mac first.[[/note]]
** There was originally going to be a film of the game directed by Creator/NeillBlomkamp, the director of ''Film/{{District 9}}''. Of course, ''District 9'' was only made because Blomkamp couldn't do the ''Halo'' movie; if there had been a ''Halo'' movie, we might be lamenting the opposite situation.
** Bungie tried and failed in each of their numbered games to get the Engineers in, but programming and rigging led to them being cut each time until they finally debuted in ''ODST.'' Per Halo 2's commentary track, they would have been seen in the intro as Arbiter is branded, floating around like a popcorn dispensery.
** There have been a number of cancelled games and rejected pitches throughout the franchise's history:
*** ''Halo DS'' was pitched by an unknown studio as a ''Halo'' game for the UsefulNotes/NintendoDS, with a proof-of-concept demo featuring the multiplayer map "Zanzibar" from ''VideoGame/Halo2'' running on the handheld ''VideoGame/GoldenEyeRogueAgent'' engine. If it ever was seriously pitched to Bungie, it never went any further than that.
*** ''Halo: Chronicles'' was a game developed by [=WingNut=] Interactive, a studio created by Creator/PeterJackson, and intended to serve as a companion-piece of sorts to a ''Halo'' film he was also attached to. It would have focused on an ordinary Marine who had an alien arm grafted onto them, which slowly turned them into a Forerunner warrior. Gameplay was built around that transformation, as the player gradually unlocked new abilities that enhanced their mobility and combat skills. The game was ultimately cancelled when Peter Jackson's involvement in the troubled ''Halo'' film came to an end. ''VideoGame/Halo3ODST'' was created in its place and incorporated some of its gameplay ideas, while the Forerunner warriors, Prometheans, would make their debut in ''VideoGame/Halo4''. Meanwhile, the 'human is given an alien arm that slowly takes over their body' idea found its way into ''Film/District9'', which was a direct successor to the cancelled ''Halo'' film project.
*** ''Titan'' was an MassivelyMultiplayerOnlineRolePlayingGame game set in the Forerunner-era developed by Creator/EnsembleStudios, who created ''VideoGame/HaloWars'' after the project was cancelled.
*** ''Haggar'' was the WorkingTitle for a game by n-Space based on the Mega Bloks line of ''Halo'' toys, which would've seemingly played like a cross between the VideoGame/{{LEGO Adaptation Game}}s and ''VideoGame/BanjoKazooieNutsAndBolts''. It was cancelled around 2013.
*** Creator/CreativeAssembly made a rejected pitch for a ''Halo Wars 3'' shortly after the release of ''VideoGame/HaloWars2''. The pitch focused on the idea of space battles, with the ability to upgrade specific parts of your capital ship to affect its performance in battle.
*** ''Halo Online'' was a free-to-play multiplayer game based on ''VideoGame/Halo3'' exclusive to Russia and developed by Saber Interactive (who handled the graphics of both ''Anniversary'' games), which was cancelled after its closed beta. It is most infamous for a FanRemake named ''[=ElDewrito=]'' that was created after its cancellation, which was shut down a few days after its first release by Creator/ThreeFourThreeIndustries. In a happy ending, 343 cited the existence of the ''[=ElDewrito=]'' project as a major factor in their decision to port ''The Master Chief Collection'' to the PC, and even consulted with the ''[=ElDewrito=]'' developers when doing so. In addition, several armor customisation options and maps created for ''Halo Online'' would make their way into ''MCC'', where they are integrated into ''Halo 3''.
*** Early in the development of ''VideoGame/HaloInfinite'', 343 Industries held an internal game jam to brainstorm ideas for future ''Halo'' gameplay experiences. The one pitch from this event to become publicly known is ''Halo: Starfighter'', a space combat simulator that would've essentially been the well-received "Long Night of Solace" level from ''VideoGame/HaloReach'' expanded into a full game. This pitch caught fan's attention when concept art for the game was included in a banner on the 343 Industries website, and it was finally confirmed to exist when the embargo for ''Halo Infinite'' concept art was lifted and several pieces made for the pitch was released.
----