These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
GLaDOS: Did she really delete part or all of Caroline? If she did, was it just a matter of deleting Caroline's memories, or did she murder an actual consciousness? Or was it not a murder but a Mercy Kill?
Does she see Chell as her lover, daughter, friend, enemy, or some combination of the above?
How much of her crazy do we attribute to the mainframe, the personality cores, the trauma of Caroline's uploading, and/or Caroline's original personality (after all, she didn't seem to mind Cave's Comedic Sociopathy...)?
How separate are GLaDOS and Caroline, anyway? When she speaks of Caroline as a separate person, is she just trying to distance herself from emotions she'd rather not have, or is there more to it? Is it even a meaningful question now that we know her personality cores are fully sentient on their own? If they're truly separate, is that something that developed over time as GLaDOS lost her memories and had personality cores added on, or were they always two people? Did GLaDOS have a fully sentient mind of her own even before Caroline was shoved into it? If Caroline's always been a separate person, was she dormant all this time, or conscious but unable to communicate?
Oh, and is PotatOS really unable to lie? If it was true when she said it, is she still unable to lie after the extra jolt from the portal gun?
When, at the end, GLaDOS says "And killing you? Is hard.", is that because she's grown emotionally attached to Chell, or is just admitting that Chell is impossible to kill?
Wheatley: As with GLaDOS, how much of his Face Heel Turn do we attribute to the mainframe's influence? Did he really expect Chell to be killed in his escape all along, as he says in the final boss fight?
Base Breaker: Hasn't exactly sparked too big of a flamewar over it (yet), but there is definitely a Broken Base regarding Wheatley's voice. Was Valve wrong to replace Richard Lord, or did they make a good choice hiring Stephen Merchant?
The Robot Enrichment DLC. Essentially a bunch of completely non-essential skins, animations and Team Fortress 2 hats, just like Team Fortress 2. (The similarity was even noted by the TF2 team, who said they snuck in and blatantly copy pasted hats into the game against the Portal team's wishes.) And just like Team Fortress 2, people raged. The Robot Enrichment customisation is largely responsible for the user ratings on Metacritic being (out of 10), 6.5 on on Xbox, 5.2 on Playstation, and 5.8 on PC, compared to critic ratings of (out of 100) of 94, 96 and 96 respectively. (It should probably be noted that, just like the Mann Co. Store, the items are completely optional — you can unlock one flag and one hat through achievements, and none of the DLC has any effect on gameplay besides looking pretty.)
The Sixense DLC for the Razer Hydra. It's 10 extra maps with additional abilities for the portal gun that you need to buy a $140 motion sensing controller for. The extra forty is for a copy of Portal 2, and the controller thus far only comes as a bundle that can only be bought online. So if you already own a copy, you have to buy it again for some added motion controls. To say the fandom has gone ballistic would be an understatement. This isn't helped by the fact that there was miscommunication that led to people thinking this was the promised summer DLC, when it wasn't produced by Valve.
Big Lipped Alligator Moment: The turret orchestra that plays during Chell's ascent to the surface at the end of Portal 2. There is some minor foreshadowing, but it's out of the way. In Chamber 16, prior to Wheatley helping you escape, there's a vent guarded by a turret which leads to four turrets practicing. You can come up with some justifications - the lyrics seem to suggest it's GLaDOS and/or the turrets and/or Aperture as a whole bidding a fond farewell to Chell, who grew up there - but that doesn't make it much less bizarre.
Broken Base: There are two real camps of Portal 2 fans, those who find it to be an excellent game and often say it's one of the best games ever, and those who think it's far too short and the focus on Co-op and relative ease of puzzles makes it simplistic. The former are decried as newbies to the Portal franchise who don't understand what made the first game great and the latter are decried as "Stop Having Fun" Guys who can't enjoy the story.
Chell/Wheatley is growing increasingly popular. Most of the fics based off of it either involve Wheatley sometime After the End, desperate to apologize to Chell for what he did and suddenly finding a means to do so, or Human!Wheatley, typically based off of Stephen Merchant.
The GLaDOS/Chell 'ship (which was already popular after the first game) is still going strong here.
The cores are often shipped with each other. Space Core/Curiosity Core ("Spaciosity") or its rival Fact Core/Curiosity Core ("Factiosity") have become quite popular, as has Fact Core/Adventure Core ("Factventure").
GLaDOS is also often shipped with The Sniper of TF2 fame. The gag for it being that their voice actors are married in real life.
Crazy Awesome: Wheatley performing a manual override on the wall? GLaDOS being turned into a potato? Portaling to the MOON to beat the final boss? The entire game qualifies.
Disappointing Last Level: Played straight with Aperture Science of the Past section (chapters 6 & 7), then later averted with the excellently designed final two chapters (i.e., Wheatley Science). After five chapters of solid plot/gameplay progression in Aperture Science, the Disc One Final Boss twist comes about and suddenly throws you into the Aperture Science of the Past section. The testing chambers are still well made, but transitioning from test to test in wide open, insipidly designed industrial environments is frustrating compared to Aperture's simplistic elevators. Like zooming into the tiny corners of each level to find tiny, easy-to-miss portal tiles, just to reach another test chamber? You'll love this part. Cave Johnson's hilarious audio recordings make these portions somewhat bearable, but hardly excuses the poorly implemented exploration. Getting back to Aperture after the last doozy of a section is a very welcome relief, and the last two chapters are arguably the game's best. Subjective though, since there are players who enjoyed the Aperture Science of the Past chapters.
Indeed, some of the hardest-to-figure-out puzzles are the ones between tests.
Which, in true YMMV form, made some players yearn to go back to old aperture after returning to new. That's where the challenge is!
Ensemble Darkhorse: The Space Personality Core seems to be turning into this. Imageboards and Youtube comments seem to be inundated with screams of SPAAAAAAAAAAAAAAAAACE.
Cave Johnson is getting this. He got an entire DLC about him scamming the entire multiverse and features the Caves of alternate universes.
Esoteric Happy Ending: The co-op ending is very silly and upbeat, having GLaDOS finding a horde of human test subjects. Very good for GLaDOS. Not so much for the test subjects.
Even Better Sequel: In the first game, the most emotional sequence besides the boss battle is dropping a box down a hole. In Portal 2? We've got so many characters introduced and developed, that it's practically a different world entirely.
Fan Dumb: Immediately after the game's release, its Metacritic score was bombed by people complaining about its length and the completely aesthetic in-game store.
It's possible that some of this was hype backlash due to the relatively minor impact of the Potato Sack & the ARG.
Fan Haters: Portal 2 being the memetic game it is, it's no surprise that people have begun posting quotes from each character on videos featuring the actors in the game (i.e. Stephen Merchant and J.K. Simmons), much to the annoyance of people who haven't played the game.
Oracle Turret for the "different" turret you can save from the Redemption Line, since everything it says is Foreshadowing, though this comes from the developers.
GLaDOS is known as PotatOS when in her potato form, a name that also shows up in the developer commentary.
Similar to how the Adventure Core claims to be named "Rick," some the fandom has begun to call the Fact Sphere "Craig," based on the portion of his monologue where he claims that Craig is the best name, according to the world's most advanced algorithms.
Game Breaker: There's a minor example for those with the Razer Hydra motion controller. The extra features added for Sixense's map pack work in the main campaign, though not in co-op. While the tests are designed in such a way that you usually can't reach the buttons unless you can walk to them in the first place, and the gel sections generally don't need precision, the ability to place cubes at a distance does make your job somewhat easier. It also makes placing the cores on Wheatley a breeze, since your don't have to jump on the Repulsion Gel. Conversely, Thermal Discouragement Beams can be a lot harder to aim.
With the addition of the Challenge maps in the DLC, the Hydra has become a true gamebreaker. With the ability to move portals and boxes, it's possible to beat courses with less portals than should be possible (without outright cheating).
Karl Pilkington is the round-headed buffoon, not Stephen Merchant.
One of the taunt Wheatley gives for making you jump down the pit is the supposed pony farm he has down there. If only Valve knew of a certain Periphery Demographic of a certain cartoon show that suddenly was popular about the time of the game's release...
The Space!Cave universe in the Perpetual Training Initiative, where said Cave keeps getting frustrated at his subjects attempting to "uncover the conspiracy" of being in space (and often getting killed in the process) despite him mentioning they're in space every half hour. What was likely originally a reference to the big twist in Dark City has taken on a new dimension with the release of a game with a similar twist less than a year later: Inversion
It's Short, so It Sucks : Portal 2 was said in prerelease materials to have a 10 hour single player and 10 hour co-op mode. In the game proper, each mode can be beat in somewhat less than that.
Cave Johnson. We get to listen to him descend into bitterness and despair shortly before his death.
Wheatley, that lovable idiot, floating in space potentially forever. He says he's sorry, and how much of it was ever really his fault?
GLaDOS. Apparently spent the time between games reliving her own destruction over and over and over again, if you believe her own report. Has her head painfully ripped off her body while she screams in horror. Attached to a potato battery purely as humiliation. Has to listen to someone she knows to be a complete moron gloat about his victory over her and watch him ruin her beloved facility. Oh, and we find out how maddening the influence of the personality cores and the mainframe must have been all this time. And that's without even getting into the whole Caroline backstory, which is pretty sad and traumatic no matter how you interpret the details.
Memetic Badass: The Adventure Core. Also something of a Memetic Sex God, due to his claims of having a black belt in everything, including Bedroom. In fandom, he's typically portrayed as being an Anything That Moves guy, being too confident in his own masculinity to really give a crap about the gender of the other.
"They told me that if I made up any more of these memes, I WOULD DIE!"
"Gla-tato," "Potat-OS" and its variants seem to be worming their way into this category as well.
Misaimed Marketing: The advertising, tie ins, and just about everything heavily tout Co-op, yet what is this huge page about? Not to mention according to only about half of PC Portal 2 players even start co-op, and only a fourth finish.
Needs More Love: Not this game, but the group of indie games being promoted as part of Valve's marketing campaign to get Portal 2 released early. Didn't result in a significantly early release (about ten hours for Steam download), but it definitely succeeded in getting those games some love.
Newer Than They Think: The "Cara Mia" Turret Opera, though you might think it was some old aria the developers borrowed for the sake of a big finish, was actually written for the game by composer Mike Morasky. Ellen McLain (a trained opera singer) used her knowledge of Italian to come up with the lyrics herself.
Robo Ship: The two cooperative mode robots were being shipped together by fan-artists before we ever saw videos of them. Images like this◊ helped.
Scrubs/"Stop Having Fun" Guys: Admittedly, it's fun to mess around with cheats every once in a while, but then you have a staggering amount of Jerkasses who will only play co-op with cheats enabled and deride anyone who doesn't want to use them.
That One Achievement: "Professor Portal", which requires you to play through the co-op Calibration Course with a friend (as in an invited one) who has never played before, is the bane of everyone looking for 100% completion. There are threads on every dedicated forum searching for people who qualify so others can unlock the achievement. It has the third lowest completion percentage of all achievements, trailing behind "Friends List With Benefits" (hug three friends) and "Still Alive" (complete Course 4 without either player dying).
Speaking of which, "Still Alive" is rather difficult to pull off, even with two players that communicate well. Most of the chambers punish screw-ups with death, forcing you to go back to the first chamber and start again. The final chamber is all that and more, since it's filled with turrets, spikes, and pits.
Visual Effects of Awesome: They did an incredible job of giving Wheatley so many facial expressions—and he's just a robotic eyeball!
Hardly surprising it's such a good job, though- the character animator for Wheatley when he's a core is none other than Karen Prell, a Muppeteer and the performer and voice behind Red Fraggle.
The destruction of your "hotel room" in the opening. Check out the commentary bubble after the scene and see just how much work was put into the one sequence; nearly nine months' worth of effort.
It's hard not to feel bad for those Frankenturrets. Especially when they look at you with big eyes, shivering after you picked them up.
The defective turrets. They're blind, bulletless, casing-less, and fully aware they're defective. You also have to feel kind of sorry for the functional turrets that get rejected, shouting, "I did everything you asssskeddd" as they get incinerated.
The "Space" Core. All it wants is to go to space. And it gets its wish!