Is he just malfunctioning like the previous animatronics or is he possessed by the vengeful spirit of the murderer? There are also theories that the murderer in that suit is somehow still alive.
The speaker sounds you use to move to manipulate Springtrap's travel are the "Hi" and giggling of Balloon Boy from the previous game. Is Springtrap just following his function to entertain children? Or is the killer looking for another victim?
Some fans like to see Springtrap (as in, the animatronic) as a sort of unfortunate victim, or even a Hero with Bad Publicity, considering he seemed to put the killer down, at least for a while. You'll see artwork that shows him as almost having puppy dog eyes, as though the mascot figure itself is the true tragic figure. Conversely, you can find artwork that play up his nightmarish design so hard that he looks less like a rabbit and more like a jackal.
The ending of Sister Location adds an entirely new perspective to him: If he's really the (presumably) innocent son of the murderer, are his pleads for help and sounds of pain genuine? What if he really is looking for help, yet his sudden appearances in the office give the guard a heart attack? This has been jossed by Scott.
The nature of the hallucinations: are they just caused by the shoddy ventilation system and the guard's fear of the animatronics, or are they related to the children the murderer killed? If they are the children, than that gives another one where after completing Nightmare Mode, a news article appears saying that the attraction burned down. This can be either interpreted as the faulty wiring (which was foreshadowed), the guard committing arson for one reason or another, or the spirits of the children themselves burned the place down.
The Fazbear Frights Guard and if you interpret the subtle hints that his playing the between-night minigames was the direct cause of putting the restless souls of the missing children at peace and/or that he was the one who set fire to the attraction, or if that was all just coincidence and he is just a First-Person Peripheral Narrator who can only observe and try to survive like the guards from the other games.
As of Pizzeria Simulator, there's a theory that the protagonist of this game is the Cassette Man, due to the similar endings (Purple Guy burning, and when it failed, he ensured that it worked the second time, making it seem he was mostly after his old friend). It would also explain the phantoms being from different eras; he remembers them all. Not to mention that he is the only guard the puppet doesn't just kill when she reaches him. On the other hand, he should be really old by the events of 3 if this were true.
The trailer's music, which encapsulates a sinister mechanical atmosphere from the get-go and stays there.
"Don't Go" that plays after you've successfully beaten all of the mini-games correctly and you go back to watch the final scene of Night 5. It's a very soothing melody that well represents that the spirits of the murdered children are finally at rest after so many long years of haunting the animatronics.
When left to play, the title screen certainly qualifies.
Contested Sequel: The FNAF fanbase is fairly polarized at this point; some argue that the game's innovations and twists on the algorithm made it a breath of fresh air, but others state that the jump scares are becoming more wooden and predictable than ever before, and that the game showcases signs of sequelitis due to how seemingly rushed it was.
Springtrap looks like a corpse, has Glowing Eyes of Doom, and contains the murderer's body. He also has a cool design and is the most brutally violent of the animatronics, not counting 4.
The phantoms as well, being damaged, burned versions of the classic and toy animatronics.
Demonic Spiders: Phantom Puppet. He leaves you completely defenseless for about 15 seconds, during which Springtrap can make a ton of progress through the building or climb through a vent unobstructed. And as if that wasn't enough, he disables your ventilation AND your audio, resulting in a grand total of about 21 to 24 seconds where you can't do anything against Springtrap. On night 5 or night 6, this is more or less fatal.
Foe Yay: Springtrap's persistence with the guard can be seen as an extremely creepy and one-sided variant of this.
Genius Bonus: As with previous games, Scott has cleverly hidden some well-known classical music pieces:
Also counts as a "Funny Aneurysm" Moment - like Foxy's jump scare in the first game, people thought Balloon Boy wasn't that scary in his first appearance. Scott fixed that◊, just like he fixed Foxy's attack in the sequel.
Springtrap's pre-release nicknames "Hybrid" and "Salvage" are still accurate post-release, as the game provided different contexts. Springtrap is a hybrid, not of combined suits, but of a costume and an animatronic, and he wasn't salvaged from parts at Freddy's, but rather, appears to have been salvaged from the Fazbear's Fright fire.
Not only that but he's also part animatronic, part human.
The initial assumption prior to 3's release of Springtrap being several animatronics combined into one is amusingly accurate in hindsight, given what the Final Boss of Sister Location is.
During a play of FNaF3, Achievement HuntersGavin Free and Michael Jones wonder about what Purple Guy is after beating the third night (and getting Chica killed). Michael says he looks like "a purple mummy". This, as it turns out, is really not that far off the mark at all, now that Sister Location is out.
It Was His Sled: Even those who haven't played the game are aware that ol' Springy's William Afton himself due to how important he is in the lore and his larger role in later games.
Memetic Mutation: People trying to find a Sequel Hook by messing with the contrast of an image of Freddy's hat posted to Scottgames.com sometime after the game's release. Many pictures supposedly contain hidden words or images in the pictures, but it's clear that it's not intentional. This died down once an actual sequel was announced.
While she's supposed to be scary, some people think the vertical burn marks on Phantom Chica make her look like a watermelon.
Springtrap is scary most of the time... except for when he's peering into the room. It looks more like he's perving on you than about to attack you. Also, most of his kills make him look like he's merely checking you out rather than attacking. On the other hand, he's the spirit of the child murderer.
Phantom Freddy creeping around outside of your window. He looks like a cartoon villain sneaking around. Just don't watch him directly for too long.
As usual, Golden Freddy can randomly appear in your office, but this time, it's off to the side and does nothing at all, appearing to be just as inactive as the other parts around the building.
Freddy has a habit of appearing through the window and just hobbling slowly to the door. Made even more amusing by the fact that if you open up the cameras or the computer, you will soon only be able to see a tiny bit of him out of the corner of your eye.
Rescued from the Scrappy Heap: Balloon Boy is now just about as terrifying as, say, the Puppet or Springtrap itself, if not slightly worse. Also, he jumpscares you now.
Rewatch Bonus: After playing the game to completion, take another look at the trailer. It flat out shows what appears to be someone's death, but you won't realize it until you see the game's ending.
The text even functions in the same way. It features twitching yellow letters in a more Retraux style that suddenly turn red with a pool of red lines appearing underneath them, much like the style in which the death was rendered.
A fairly popular fan theory before the game's release was that Phone Guy was the killer. This game makes it extremely unlikely, as he canonically died before the murderer did, but a good number of fans still insist he's the killer anyway.
In a further Broken Base on the topic, there's even an argument over whether Purple Man died before or after Phone Guy, depending on your interpretation of the timing of the safe rooms being sealed.
Fans continue to run with this, even after the Murderer is revealed in Sister Location to be an Evil Brit, meaning he's very likely not the Minnesota Nice Phone Guy.
The Phantom Puppet follows your gaze and blocks your vision, but it skips while it follows your head turning. Instead of it being smoothly frozen in front of your face, it looks like it's sliding, dragging, or limping across the floor. This was likely intentional, though. If anything, it makes the Puppet even creepier. Compound with the threat of Springtrap lurking near you office, and you got a pretty unsettling combo.
The Office is a rectangular room that's too big to see without the player turning their head. Unfortunately, the mechanics of the head turning make the room look curved.
During the between-night minigames, it's possible to make it so The Purple Guy rushes through a wall or the boarded up doorway.
That One Sidequest: If you want to get the good ending on the mobile version, you'd better pray that you don't screw up any of the minigames, especially STAGE 01, since all of them apart from BB's Air Adventure aren't selectable whenever you wish, having taken the place of the post-night minigames. Fail to gain the cake ending on any of them and you'll need to restart from night one. It's also a lot easier to screw yourself over due to the altering of the stages and the removal of the jump button.
Ugly Cute: In a weird way, Springtrap. The way it crawls around the vents is kind of cute, and its Slasher Smile looks more like a big, goofy grin in some shots. Although who Springtrap really is isn't so cute.
Springtrap seems to be more articulate in its facial expressions than its predecessors. Also there is just something a bit too lifelike about its eyes. The fact that it looks like a stitched-together corpse does not help. As it turns out, there's a good reason for all this...
The same argument could be made for the Balloon Boy teaser, particularly since he looks like he's drenched in blood. And still with that ever-present grin.
...Really guys? You wanted to make an attraction based off the Fazbear legends? The description for the game says that whoever developed this managed to get a hold of an actual animatronic, which implies they underwent some sort of research in order to get said machine. Which means that they had to have realized that this not only really happened, but that chances are those animatronics aren't good news... and they still thought it was a good idea to go through with this?! Hell, even if they were skeptical of the supernatural elements, wouldn't they be hesitant to do this on the grounds that they'd essentially be making The Theme Park Version of a dark and messed-up tragedy that cost quite the amount of lives, while also profiting off of said tragedy? It either comes off as completely foolish with the former or completely callous with the latter, or even both.* It's actually not that unheard of to turn a profit off a horrible tragedy; just look at cases involving Lizzie Borden, Jack the Ripper, or even the Titanic. Although, even with it having been 30 years in the past, creating a horror attraction centered around a child murderer, urban legends of haunted animatronics or not, could still be considered in very poor taste.
To a lesser extent: the new security guard, or guest, being completely Genre Blind and accepting to stay in this place which caused so much danger to those that worked the night-shift.
The management is right up there (which seems to be a theme in the FNAF games); they purposely use faulty wiring in their attraction in order to make the horror-theme more authentic, but even worse, they know the ventilation system doesn't work and if it shuts off, it can cause patrons to hallucinate. It's so bad even a single person suffers from it, let alone thinking what it would do to a whole group of paying customers. Such an oversight is a blatant lawsuit waiting to happen.
Fazbear Entertainment almost had another instance of this trope on file. There was a period where they tried retrofitting the animatronic suits to fit humans and robots alike. The human settings were so badly designed that they could crush the person wearing it if he so much as breathed wrong. After one implied casualty, they hastily dumped the idea. It bears repeating that Fazbear Entertainmentthought this was a stupid idea, to the point Jeremy and Mike never heard about it.
A Subversion. Before the release of Sister Location Purple Guy's actions in the minigames could have been considered outright idiotic, as he decided to return to the scene of crime seemingly without reason. Sister Location heavily implies that he sent his son to find and repair something, and presumably take the fall for him. Pizzeria Simulator josses that, but implies that he knew that dying in the Springtrap suit would enable him to continue to live as Springtrap!