!!''VideoGame/{{Portal}}''
* The ending song jokingly and mockingly references [[VideoGame/{{Half-Life}} Black Mesa]]. Songwriter JonathanCoulton also namedrops another of his popular songs, "I Feel Fantastic".
** [[VideoGame/{{Half-Life}} Black Mesa]] is also referenced in several slide shows left running in staff areas that are accessible or at least you can see into easily.
* Doug Rattmann's den in the Companion Cube level also contains a rather well-hidden shout out to Creator/IsaacAsimov's short story "Escape". His dens all have some poems altered to include cubes and the like. [[http://half-life.wikia.com/wiki/Doug_Rattmann#Graffiti_list Here]] is a full list of the graffiti drawings.
* "Delicious and moist" cake was originally a joke in ''VideoGame/{{Psychonauts}}''.

!!''VideoGame/{{Portal 2}}''
* You can find a drydock, with a life preserver titled "Borealis" next to it. The ''Borealis'' is where [[VideoGame/{{Half-Life}} Gordon Freeman]] will likely go next in the series.
* Cave Johnson implies that Black Mesa has stolen more than one of his inventions.
-->'''Cave Johnson''': Black Mesa can eat my bankrupt-\\
'''Caroline''': [[CurseCutShort Sir? The testing?]]
* One of the displays in the old Aperture Science lobby also holds a series of awards. One diploma for the #2 spot on the top 100 list of the applied science companies of 1949, and two trophies (from 1952 and 1954) for the runner up of the "US Dept. of Defense Contractor of the Year". No points for guessing [[VideoGame/{{Half-Life}} who took first place]].
* Another Asimov reference states that all turrets were given a copy of the [[ThreeLawsCompliant Laws of Robotics]]. [[FalseReassurance To share]].
* There's a science experiment that resembles a [[Film/BackToTheFuture Flux Capacitor]].
* The trailers show a line-up of turrets, one of which proclaims [[Series/MysteryScienceTheater3000 "I'm different..."]]
* [=GLaDOS=] says "Yesterday I saw a deer" at one point, referring to ''TheDandelionGirl''.
* In the ending, something flat (the monitor screen) flies by and Wheatley drifts forward, much like ''Series/TheTwilightZone'' opening credits.
* A DummiedOut line from co-op mode's original plot involving [=GLaDOS=] trying to get Atlas and P-Body to behave more like humans involved them bringing back a comic strip about [[ComicStrip/{{Garfield}} a cat who freeloads in a man's house and eats all his lasagna]]. [[SeinfeldIsUnfunny She's not very impressed]], and [[Webcomic/GarfieldMinusGarfield decides to rework it]].
* One of the Achievements is called "Narbacular Drop", a shout out to the student project that eventually became ''Portal''.
* The Bots trailer features Atlas [[http://www.youtube.com/watch?v=W_gxLKSsSIE holding a frying pan with a pancake]]. A bit of a TakeThat with Atlas [[http://www.youtube.com/watch?v=AZMSAzZ76EU just not doing it right]].
* One of the Fact Core's facts is [[Series/{{SCTV}} "In 1948, at the request of a dying boy, baseball legend Babe Ruth ate seventy-five hot dogs, then died of hot dog poisoning."]]
* In the comic, Chell's file states her test subject number as 1498, [[Manga/TwentiethCenturyBoys as well as a certain imprisoned mangaka]].
* Caroline's line "Goodbye, Caroline!", to LaughIn, which always ended with "Say good night, Dick!" "Good night, Dick!". Ironically, it was likely intended as a ShoutOut to the BurnsAndAllen Show instead, since legend has them ending the show with "Say good night, Gracie!" "Good night, Gracie!". However, Burns and Allen [[BeamMeUpScotty never actually used that line]]. Burns and Allen would have been on the air when Cave and Caroline made their recording, and LaughIn did not start until 1968, so it's more probable that the writers meant it to be a BurnsAndAllen reference.
* One of the co-op achievements is called [[Music/{{MC Hammer}} "Can't Touch This"]]
* In one of [=GLaDOS=]'s new test chambers, she says that the test chamber Chell is in requires explanation. Being [=GLaDOS=], she gives it rather quickly, and then tells Chell to "remember what [she] just said in slow motion." If you actually ''do'' slow it down, you'll find out that is actually a passage from ''Literature/MobyDick''.
* When navigating through the manufacturing factory with Wheatley, he off-handedly starts telling a ghost story. [[Film/TheShining "They say the old caretaker of this place went absolutely crazy, and chopped up his entire staff...of robots."]]
* Screaming, '''"I AM NOT A MORON!"''', reading philosophical books, and basically being a vengeful idiot who thinks he's a genius, yes, Wheatley has more than a little [[Film/AFishCalledWanda Otto]] in him. Confirmed by WordOfGod.
* From the Blue Screen of Imminent Death: "OPERATOR ERROR. [[VideoGame/WorldOfWarcraft MOLTEN CORE]] WARNING."
* From the Peer Review DLC: "Ahem, [[Creator/WaltDisney if you can dream it, you can]]-- oh for god's sake..."
* Rick, the Adventure sphere says that he's got a belt in just about everything, from Karate to [[http://www.teamfortress.com/war/saxtonhale/poopyjoe.htm Larate]].
* One of P-body's dances makes her do a spinning dance, before stopping and shooting a Portal straight forwards. This may be a reference to the dance the Wizzrobe from ''VideoGame/TheLegendOfZeldaMajorasMask'' preforms before attacking Link.
* Cave Johnson's name ''might'' have come from that of one of the characters in the 1981 film ''The Bushido Blade''.
* If you let Wheatley talk long enough in the Neurotoxin Control Center, he'll try to distract the computer by mentioning a bird with [[Creator/MontyPython gorgeous plumage]].
* The achievement for smashing all of the monitors of [[spoiler:Wheatley]] is "VideoGame/SmashTV".
* In the two player game there is a sequence where one of the players has to go across a path while the other player throws switches to raise and lower platforms for them to get across. This is how the old NES game Gyromite was played, wherein your robot friend would appraise the situation and raise and lower platforms for you to walk across.

!!''Portal 2 Perpetual Testing Initiative''
* In the Website/YouTube promo, Cave Johnson starts off talking about his father, "a Professor of Farming at the local Farm College." Cave Johnson's voice actor, Creator/JKSimmons, appears in a series of commercials for Farmers Insurance as a professor at the fictitious "University of Farmers".
* One of the [[TheMultiverse parallel Caves]] mentions Film/SoylentGreen.
-->'''Cave:''' Memo says [[ItWasHisSled Soylent Green is]]...let's see...[[BaitAndSwitch doubling in price.]] Now, I don't care how good [[ImAHumanitarian people]] [[SubvertedTrope tastes]], it's costing us more than lobster so we're all going back to fish-sticks.
* Another parallel's apparently working on [[Franchise/RoboCop the world's first half-man, half-machine police officer]], [[LawyerFriendlyCameo Roboticop.]]
* And in another they successfully create psychics [[Film/{{Scanners}} who blow people's heads up]]. Cave gets back at them by taping their paychecks to the negotiator's head in a psychotic act of CrazyPrepared.
* Immediately after that, Cave Johnson wishes you a happy birthday, then mentions [[Film/{{LogansRun}} government compulsory maximum age]].
* And in yet another Cave complains about [[Film/TheyLive magic sunglasses that let the wearer see subliminal messages on the walls]].
* An...altered version of ''Literature/WutheringHeights'' gets a mention (specifically Heathcliff fending off the titular [[RecycledInSPACE moonbase]] from vengeful poltergeists. Virginia Woolf and the Brothers Karamazov get a name-drop too, as part of computer!Cave's [[WhoWantsToLiveForever boredom-staving exercise]] of adding [[Film/{{Ghostbusters}} Ghostbusting]] to every work of fiction.
* And there there's "Cave Johnson here. Just a reminder that the core goal of Aperture Gas-Finding Science is to find gas, so make sure you let us know if you see any. If we meet our quarterly gas-finding target, I promise you we will don our bondage gear, fuel our death cars, and drive around in circles, whooping it up and shooting arrows at people. Who is ready to rule the wasteland? Alright, start looking". ''Film/MadMax'' anyone?
* And then of course, there is ''Film/SmokeyAndTheBandit'' Cave, who has you test on your own while he goes to Texarcana and back in 28 hours.
* One universe finds itself stuck in ''Film/InvasionOfTheBodySnatchers'', though Cave decides to do nothing about it, because aside from the kidnapping, they're pretty much harmless. If the worst they can do is gestate glassy-eyed Yes Men, then bring it on, Bug-Eyes.
* Another universe features a demented Cave that sounds like he's staring at you from under a sewer grate, [[Literature/{{It}} threatening to dismember you.]]
* In another, Greg's son takes over the mike and says, "Hi down there, we're gonna test forever...[[Film/TheShining and ever and ever.]]" Then Cave bursts in and shoos him out, telling Greg that [[CreepyChild "There is something wrong with that kid."]]
* In yet another parallel, Cave Johnson mentions [[Podcast/{{WelcomeToNightVale}} a sentient cloud]] that's Earth's governing body.
-->'''Cave Johnson''': [[Podcast/{{WelcomeToNightVale}} All hail the sentient cloud. Begin testing.]]
** This is also a CallBack to when the Announcer mentions in the main game the Earth being governed by a "sentient cloud" as a potential post-apocalyptic scenario.
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