WMG / Willy's Wonderland

The Drifter has been to Willy's Wonderland before.

If this picture is still canon by the time the movie comes out, then the kid is who the Drifter used to be. He lost his family in Willy's, and has been drifting from state to state ever since. He's also been training in hand-to-hand combat, or perhaps enrolled in the army, and that's what allows him to hold his own against the animatronic killers.

When he sees he's back in Hayesville, he takes the job, knowing the animatronics are alive and bloodthirsty, so he can get revenge against the animatronics for taking his family from him.

The Janitor is fey, such as a Brownie.

He's bound by (verbal) contracts that he follows to the letter, lives off of sugar drinks (soda instead of the traditional honey), never speaks, and is preternaturally good at cleaning.

• In support of this, he never touches cold iron. The road spikes are steel on a rubber strip, the only metal he uses cleaning is aluminum buckets, the 'Punch! Cola' cans are aluminum, he doesn't use any kind of metal weapon, the cabinet of the pinball machine is wood ^note  According to the site 'Pinball Castle' with an aluminum frame and plastic buttons, and (as far as my research extends) the Camaro he drives is a steel body with aluminum frame wheels and engine.
• Some of the cleaning scenes, such as the bathroom, are filmed as Undercrank... or are they? Maybe he's just that fast when he gets his magic cleaning mojo running.

The Janitor was a kid

Who realized the truth and wanted to take down the BASTARDS.

Liv wasn't killed

Because they never found her. That's why the bots knew her name and seemed especially desperate to kill her. She was the one who got away.

The Janitor is a relative of Red.

As either a younger brother or a nephew, the Janito grew up hearing stories of Red's crazed encounters with bizarre, demonic forces, and thus isn't surprised when he encounters some of his own. He also shares Red's exceptional combat prowess, affinity for immaculate shirts, and drinks soda as a possible nod to Red's alcoholism.

• Alternately, he may be a descendant of One Eye, Mads Mikkelsen's character in Valhalla Rising. Both are mute, unstoppable warriors.

The Janitor is Red.

The events of "Mandy" left him A) nigh-immortal and B) particularly susceptible to contracts.

• He's still burned out from what happened 30 years ago; his social skills never fully recovered, to the point that he doesn't communicate much. He will also not pass up an opportunity to stop the machinations of yet another cult, the likes of which he's come to recognize (albeit too late to make any kind of decision about it, this time).
• Tying in with the likelihood that Red's a recovering alcoholic, The Janitor loves him some sodas.
• Following from that "the Janitor is Fey" theory above, some aspect of his Ambiguously Human nature means a promise or contract is closer to Magically-Binding Contract that he can't ignore. Thus, the care taken to take breaks, no matter what is trying to kill who at the moment.
• In exchange, the contracts he agrees to power him up like a Geas. He gets superhuman cleaning ability, and anything that gets in his way or prevents him from accomplishing his side of the bargain gets "cleaned" as well. (Almighty Janitor indeed!)
  • Because all he can do is clean and take breaks, it affects how he interacts with the teens. Disarming Liv counts as preventing a bigger mess of one kind or another. The flip-side of this is, if the teens made any kind of mess (like Liv trying to stabbity-stab) or got in his way, he might have to deal with them like he does the Animatronics.
  • The damage they did to the roof doesn't fall under "cleaning Willy's Wonderland", because he's the Janitor, not the Carpenter. The debris from their entry doesn't count as something he needs to clean, either, because it fell into the ball pit, not "Willy's Wonderland".
• And all this is why he's a drifter: too many chances to cause collateral damage, but he's drawn to the sorts of situations where his presence is required. Eventually he'll run into a Religion of Evil that requires his distinctive presence.

The Animatronics want to die, even Willy.

But their ritual gave them the compulsion to feast on the living, at first, they had no issue with it, but as time went on, they are stuck in the Restaurant (they seem strong enough that something must be keeping them there), with only the occasional drifter or family the town throws their way, along with the fact that their bodies are clearly degrading, Willy didn't know that the ritual binds them to him, so they act like typical slashers despite being able to Gang Up on the Human from pretty early on, they are still obeying Willy, but they actually hoped someone like the Janitor would come along, because they actually hate being stuck like this.

• It might explain why Siren Sara blew up Tex and Jed, even though she must have known she was sufficiently damaged that she couldn't move fast enough to escape the blast herself. She wanted to go out in a blaze of 'glory', and she secretly despised the humans who fed the animatronics, instead of destroying them. (after all, if Tex was willing to lose the building completely it could have been done. Maybe filling the boarded-up building with gas via the rooftop air vents and blown the place?)

The Janitor is a member of the SCP Foundation.

• His military service and hand-to-hand combat skills led him to a career as a Foundation agent. He's Seen It All due to having captured and restrained various anomalies, and doesn't speak due to some prior experience with SCP-939 or something similar.

The Janitor is autistic.

A lot of the Janitor's odd behavior could be explained by him being autistic. Namely:

• He has a routine he will follow at all costs.
  • This primarily manifests in the exactly 15 minute breaks once an hour, but is also noticeable in the fact that he drinks one can of the same soda every time before crunching the can and throwing it away.
• When given a task, he has a compulsion to finish it, and is very detail oriented about doing so.
• He doesn't seem to understand or read the social cues from the others (particularly Liv) about the gravity of the situation (but still covers their corpses out of respect). He also doesn't seem to fully understand what's socially appropriate (i.e. the dancing scene, engaging in his routine regardless of circumstance).
• He is nonverbal.
  • Many autistic people are nonverbal/mute. This does not impact ability to understand spoken language (and is not, as many people assume, tied to a lower level of functioning). However, it does make it difficult for the autistic person themselves to verbally communicate despite having functioning vocal cords.
• He might alternatively be a highly trained soldier with some form of OCD, like Robert McCall in The Equalizer.

There are other Willy's Wonderland restaurant's.

• Willy's could have a chain of restaurants all over the country, let's hope their animatronics aren't demonically possessed as well.
  • Doubtful, unless Willis lead/was part of some kind of country/worldwide network of murderous cannibals.
  • Some serial killers in the past have often killed victims in multiple states in order to avoid being caught. If the franchise founder started in the 1984, then after committing several kills in one state and the police start to notice, he probably relocated to open another franchise restaurant elsewhere, committed more kills and then relocated again after police starting to look into there. And Liv stated that that the guy who possessed Willy was the founder (which typically is reserved for franchise founders), and answers why the theme song says it's been entertaining familes since 1984 when Liv says the restaurant was built in 1996: that particular place was opened in 1996 while the franchise itself has been around for a while.

Sheriff Lund has been taking advantage of the Deal with the Devil to maintain her grip on law enforcement power.

Liv and her friends can't be the first people who had the idea to destroy Willy's Wonderland. Were the people of Hayesville that terrified after the -no-demolition massacre? Was the teen's lack of self-defense weaponry (this is America, land of gun worship, after all) just one more aspect of their Too Dumb to Live? Or did Sheriff Lund use her power as Sheriff to make sure no kinds of useful weapons could be sold within the county? (The gasoline Liv uses was possibly the only thing in too widespread use to be controlled) And did she make sure no one got any bright ideas by arresting them and throwing them into Willy's handcuffed and defenseless? Sheriff is an elected position... wonder if anyone who thought about running against her 'disappeared'?

The Janitor is the protagonist of a Five Nights At Freddy's-like video game, and everyone else is an unaware NPC

He doesn't speak because he's a Heroic Mime, the mandatory 15 minute breaks once an hour are built into the structure of the game as an Acceptable Break from Reality, and the soda is either a Power-Up item or a Save Point. The other eccentricities of his actions could be signs of a player who's already played through the main story and is now trying for a specific ending that requires cleaning the restaurant perfectly, but also letting everyone else die. The pinball game is a mini-game within a game, and he knows he can sit around and play pinball all he wants without any of the animatronics interrupting him.

The Punch Soda isn't actually Soda.

It's an experimental super serum, that only lasts short doses, hence why the Janitor has to take the breaks, because the Janitor has worked out exactly how long the serum lasts, with the side effect that it makes the drinker mute, he actually works for an agency that deals with places like Willy's Wonderland, hence why he has a supply of the stuff, he knew what was going on and had to make sure he stayed supercharged.

Soul transfer wasn't the only boon Willy's coven received.

They seem just as shocked as anyone that actually fighting back works perhaps they received boosts of some kind regarding how dreadful they seem to their victims, perhaps to the point of lifting cars or becoming bullet-proof if someone is scared enough.

The Animatronics have some way to self repair.

They did come back from the dead that one time perhaps the supernatural mojo that keeps them going will do so again.

If FNAF ever becomes a movie...

... The Janitor will be The Phone Guy.

The Janitor is Seth from City of Angels.

After death of Maggie, Seth decided to dedicate his life to hunting down evil spirits. As former angel, Seth is still well beyond the limitations of ordinary humans - hence his martial prowess and super strengh. He is unfazed by horrors happening in Wonderland because of both his own spiritual origin and experience as vigilante/paranormal investigator. His lack of social skills culd have beign explained by both lack of time to adapt to normal life.

Tito survived.

Notice how unlike other animatronics, his head remained relatively undamaged. It worked previously for Sara... It's possible that after some repairs, he could be reactivated with his memories and personality intact.

The Big Bad in the sequel will be Satan in an animatronic.

The Janitor is a player character, and the movie is any% speedrun.

The Janitor is not interested in lore and other characters simply because the player already finished game before. He tries to end any fight quickly - and avoid them if possible - to save precious time. And he knows that he don't have to kill all Animatronics to get good ending.

The film takes place in the Five Nights At Freddys universe.

Willy's Wonderland is a restaurant created to act as a competitor for Freddy Fazbear's Pizza, but was never as popular. Robert Willis was secretly idolizing William Afton, and when rumors spread out of him killing children, him and his crew began doing the same to be like him... And they did.

Sequels will have The Janitor fight other monsters.

Guesses can be added here:

• A Jason Voorhees expy.
• A Leatherface expy, accompanied by expies of Leatherface's family.