Note: Entries for the first game should be on its own [[YMMV/Portal1 YMMV page]]. For ''VideoGame/{{Portal 2}}'' YMMV entries, go to the YMMV.{{Portal 2}} article.

* AlternativeCharacterInterpretation:
** Does [=GLaDOS=] truly despise Chell, or does she truly care about her but unable or unwilling to express it?
** Chell is subject to a lot of this as she's a SilentProtagonist. One of the common areas of debate revolves around her silence, as there's discussion about whether she's mute, or whether she's perfectly capable of talking but just stubbornly refuses to give the insane and annoying robots she's surrounded by the satisfaction of a response. WordOfGod states the latter is the case in ''Portal 1'', but ''Portal 2'' is ambiguous. Is it the same, or is she suffering from brain damage after her experiences in cryo-sleep?
* {{Applicability}}: Particularly in the first game, as [=GLaDOS=]'s dialogue provides most of the game's atmosphere and world-building. The creators have encouraged the vast numbers of EpilepticTrees about the series, and about [=GLaDOS=]' character in particular. It has provoked a lot of professional analysis and extrapolation about her meaning and symbolism. [[http://en.wikipedia.org/wiki/GLaDOS#Character_analysis See for yourself.]]
* BreatherLevel:
** After being shot at nearly every time you turn a corner and open a door in chamber 16 you immediately have chamber 17 where the worst thing you may encounter is easily dodgeable energy pellet spheres. And maybe regret over having to "euthanize" the companion cube.
** Test Chamber 19 is much shorter than the long and challenging Test Chamber 18, with more forgiving mechanics and less reaction-based gameplay. [[spoiler:Subverted, as it ends with [=GLaDOS=] attempting to drop you into a fire pit, starting the "escape" levels.]]
* BrokenBase: Virtually everybody likes both games, but there is a thankfully mostly civil debate about which of the two is superior. ''Portal'' has a dedicated fanbase who prefer its lonely, existential and grounded atmosphere, more subtle sense of humor, and its tighter pacing and difficulty. ''Portal 2'' meanwhile tends to be preferred for its stronger list of puzzle elements, significantly expanded scope and a far more expressive style of comedy and character writing.
* CargoShip: Chell/Companion Cube is a popular shipping pair in the fandom.
** The Rat Man's [[RoomFullOfCrazy graffiti]] shows he was far too attached to his CompanionCube, and really didn't take having to incinerate it at all well.
** The ''Lab Rat'' comic proves that he ''failed'' to incinerate it, carrying it around with him and even talking to it (including hallicinations of responses) in his schizophrenic mania.
* CommonKnowledge:
** "The cake is a lie" is one of the most famous things to come out of the game, to the point where it's mistaken for TheReveal. Even people who have played the game will quote it due to its MemeticMutation status, even though the end credits show [[spoiler:there really was a cake]].
** Following the release of ''Portal 2'', many people believe that all surfaces capable of holding portals need to be painted with moon dust. In truth, many other surfaces work too, such as concrete - as seen in the ''many'' test chambers for the portal gun built years before the moon landings. They just have a lot of it because Cave carelessly invested a lot of money in moon rocks not knowing they were poisonous.
* ContestedSequel: How some fans treat the sequel bridge comic "[[http://comics.ign.com/articles/116/1160605p1.html Lab Rat]]"; these fans believe that [[TheyChangedItNowItSucks adding more story to the canon detracts]] from the [[StoryToGameplayRatio original story's minimalist appeal]].
* CreepyAwesome: [=GLaDOS=], at least according to most of the internet.
** Ellen [=McLain=] talks about the experience of being [=GLaDOS=] (including a very sexy voice, an unexpected burst of opera singing, and a scary laugh). Have a listen to some [[https://www.youtube.com/watch?v=648DRxIfgx4 commentary]].
* CreepyCute: The Sentry Turrets. Sure, they’re loud killing machines and [=GLaDOS’=] most direct method of murdering you, but their computerized childlike voices, their calls for help when knocked over, and their polite way of speaking makes them seem like {{Adorably Precocious Child}}ren.
* CrossoverShip: [=GLaDOS=]/[[Film/TwoThousandAndOneASpaceOdyssey HAL 9000]]. Particularly after the two got a brief interaction in '' VideoGame/LegoDimensions''.
* CultClassic: Its popularity despite being a pack-in game for a ''Half-Life'' compilation owes itself to very good word of mouth from its fans.
* EnsembleDarkhorse: The Weighted Companion Cube. It was intended to be this to begin with in the game, but even Creator/{{Valve|Software}} admitted they vastly underestimated the extent to which it was adopted as a fan favorite.
* EveryoneIsJesusInPurgatory: There have been some truly odd interpretations of this fairly straightforward game as, among other things, a crushing feminist assault on the masculine and misogynist games industry. See the [[WMG/{{Portal}} Wild Mass Guessing]] page for details.
* FandomRivalry: A few ''Portal'' fans pointed out ''VideoGame/{{Ingress}}'' stole the ideas from the games.
* GeniusBonus: Some people have deciphered the morse code tied to the new achievement. [[spoiler: It appears to be [=GLaDOS=] [[http://www.shacknews.com/onearticle.x/62575 rebooting]].]]
* GoodBadBugs: While the ''First Slice'' demo is supposed to cut the player off after test chamber 10, some players have been able to complete chambers 11 and 12 and get the dual-portal gun. Chamber 13, however, is not in the demo, meaning players are blocked by an eye-destroyingly bright wall of Nodraw when the elevator opens.
* HilariousInHindsight:
** One of the early FinalBoss battle ideas was "[[http://www.gamasutra.com/php-bin/news_index.php?story=17625 a high intensity rocket battle with GLaDOS in a room full of turrets]]", which the team called "[[Franchise/MortalKombat Portal Kombat]]". Four years later, ''VideoGame/{{Portal 2}}'' was released on the same day as ''VideoGame/MortalKombat9'', leading to things like [[https://www.youtube.com/watch?v=uyOzzd53ssY a parody with portal-based fatalities]]. The [[VideoGame/MortalKombatX next MK game]] got a custom mode called "Portal Kombat".
** Early on in the life of the UsefulNotes/NintendoSwitch, a popular fan combination for Joycon colors was the Orange and Blue of the portals (such as [[https://www.reddit.com/r/NintendoSwitch/comments/7i2smy/created_a_lil_mockup_if_portal_ever_decides_to/ this]]). Flash forward to 2022 and both Portal games get released on the Switch.
* InferredHolocaust: Never mind all the researchers that [=GLaDOS=] gassed; "Bring Your Daughter To Work Day" implies that their ''children'' became victims too, or were tested to death. [=GLaDOS=] also manages to sneak in a reference to the multiple disasters of the ''VideoGame/HalfLife'' universe during the FinalBattle and in the "Still Alive" bonus levels. It's implied during ''Portal 2'' that Chell herself was the daughter of one of the scientists at Aperture and she was present during the massacre.
* ItWasHisSled:
** The cake being a lie [[spoiler:[[DoubleSubversion except it wasn't]]]].
** [=GLaDOS=] being a killer AI. The trailers for the sequel don't try to hide this fact.
** The fact that you end up escaping the test chambers and making your way through Aperture's backstage machinery.
* MagnificentBastard: [[AIIsACrapshoot GLaDOS]] is a computer created by [[MadScientist Cave Johnson]] to run Aperture Science after his death. Once activated, [=GLaDOS=] proceeded to kill most of the scientists with neurotoxin and took over the Enrichment Center to conduct tests at her own leisure. [[VideoGame/Portal1 In the present]], [=GLaDOS=] put Chell through a series of potential lethal tests before trying to murder her. Defeated and shut down by Chell in retaliation, [=GLaDOS=] is [[VideoGame/Portal2 accidentally awoken years later]] by Wheatley. Throwing Chell back into more tests, she is eventually overthrown by Wheatley thanks to Chell's actions. With Wheatley threatening to destroy the facility with his own stupidity, [=GLaDOS=] convinces Chell to help her take Aperture back from Wheatley, and in turn lets Chell go when that is done. Switching focus toward Cooperative Testing, [=GLaDOS=] uses the robots Atlas and P-body to secure control over the lower parts of the facility and eventually give her access to more human test subjects. When a mysterious hacker (actually a mother bird on a keyboard) forces her hand, resulting in the deaths of her human test subjects, [=GLaDOS=] sends the robots after it before adopting the baby birds to raise as killers.
* MemeticMutation: "There Will Be Cake," "The Cake Is a Lie," "Now You're Thinking With Portals," and the Weighted CompanionCube, among others. [=GLaDOS=] is officially a FountainOfMemes.
* MorePopularSpinoff: It's hard to remember that ''Portal'', which technically takes place in the ''VideoGame/HalfLife'' universe, started off as a pet project ("a little [[http://en.wiktionary.org/wiki/lagniappe lagniappe"]], in [=McLain=]'s words) that was included as a bonus game as part of the compilation ''The Orange Box''.
* SugarWiki/MostWonderfulSound: Evil though she is, [=GLaDOS'=] singing voice is beautiful.
* PlayerPunch: "Killing" the companion cube (although incinerating the companion cube is meant more as a parody of this trope.)
* PolishedPort: Impressively, the ''Companion Collection'' for Nintendo Switch runs at both a higher resolution and framerate than both of the original console versions of either, the latter even in handheld mode.
* SacredCow: Like all of Valve's games, no one will let you off easy for disliking it.
* TheShipsMotor: The ''Portal'' fandom has a habit of taking bots like [=GLaDOS=] and Wheatley, and making them humanoid, either by downloading them [[{{Transhuman}} into a human body]], [[RidiculouslyHumanRobots giving them some sort of android]], or [[ArtificialHuman finding a way to mix the two]]. This is done in part to make writing their expressions easier in fanfiction, but mainly it seems to pair them with [[PlayerCharacter Chell]]. This was only reinforced after [[spoiler:''Portal 2'' revealed [=GLaDOS=] herself [[BrainUploading used to be human]]]]. Wheatley being the more human of the two (with less [[ElectronicSpeechImpediment mechanical feedback]] in his speech, [[BadLiar truly]] [[ArtificialStupidity incredible]] [[TheDitz fallibility]], and "facial" gestures,) expect his androids and cyborgs to appear more natural, while [=GLaDOS=]'s will have wires or damage right out in the open.
* ShipsThatPassInTheNight: Gordon Freeman and Chell is a popular ship due to their ridiculous number of similarities, despite the fact that, as far as we know, the two have never met, and are currently in ''completely'' different countries, possibly even in different time periods.
* SpecialEffectsFailure: At the very end of the game, [[spoiler: when you're lying on the ground outside the entrance to the facility]], there is a backdrop of trees laid out in front of you. When [[spoiler:a robot grabs you for assuming the Party Escort Submission Position]], the movement of the screen allows you to see that the tree backdrop doesn't extend past your initial field of vision. This is because [[spoiler: the Party Escort robot]] was patched in long after the game was finished as a teaser to ''Portal 2''.
* ThatOneLevel:
** The Advanced Test Chamber 18 will have you tearing pieces of yourself out in frustration.
** Rather notably, Chamber 17 started out as one for the playtesters, as they had trouble adjusting to having to carry the cube around the whole time rather than leaving it behind after one use, and especially couldn't quite wrap their brains around using it as a shield in the opening corridors. The result was the {{Companion Cube}}.
* WatchItForTheMeme: {{The cake is a lie}}.
* WhatDoYouMeanItsNotForKids: The concept of a puzzle game with quirky humor, cake, and a metal box with a pink heart on it may sound kid friendly at first, up until the part where you learn that the psychotic AI nerve-gassed every living creature in the facility, [[spoiler:on Take Your Daughter To Work day.]]
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