According to Forbes, YouTube star PewDiePie pulled in a cool $12 million last year. If you’re asking “how the hell does a person I’m not even sure is a real ‘star’ pulling in that kind of bank?,” you’re obviously not up on the $3.8 billion “gaming video content” empire that PewDiePie is a part of. Do you remember going to a friend’s house with a bunch of your friends to play video games and having to sit on the sidelines and watch the homies playing the game, and how that could sometimes be more fun than having your hands on the controller? That’s essentially what it’s like to watch a PewDiePie video.

If you didn’t recognize it from the video, PewDiePie was playing Five Nights at Freddy’s, a survival “point-and-click” horror game that has spawned three sequels since its initial release in August of 2014, going viral on YouTube and causing the video gaming community at Steam to go nuts, not just for its chilling premise but for the deeper lore that fans are trying to suss out.

Simply put, the initial Five Nights at Freddy’s puts you in the role of a late-night security guard at a pizza place where the animatronics turn deadly after-hours. Yes, it’s like Chuck E. Cheese gone horribly wrong. You’re not in control of much; you sit in a dusty room, watching monitors from 12 a.m. to 6 a.m. trying to not get murdered. That’s it; you’re literally flipping to monitors to track the animatronics through the establishment, and if they get too close to your hub, you can close the doors (so, you know, they don’t kill you), all the while making sure that you’re conserving your power, because loss of power shuts down your entire guard station which, you guessed it, allows for the animatronics to kill you.

While you might be skeptical about this game a) being exciting or b) causing a ripple in the “gaming video content” community, think again: YouTube ranked the Five Nights at Freddy’s series at #8 on their all-time list of biggest games on YouTube, based on viewing time. Sure, that put it behind games like Minecraft, Grand Theft Auto, and FIFA, but that’s pretty damn amazing for an indie game that no one had even heard of before August of 2014. There was even a time when the first three Five Nights at Freddy’s games were in the iTunes top-ten for paid apps (primarily because the series’ creator, Scott Cawthon, dropped two sequels in a six-month time frame). That popularity is probably what piqued Warner Bros.’ interest, as they plan on making a live-action film based on the Five Nights at Freddy’s series, with Gil Kenan (Monster House, the recent Poltergeist remake) tapped to write the script.

What made the game so popular?

An important part of the Five Nights at Freddy’s popularity is steeped in the nostalgia that Five Nights at Freddy’s conjures up. Whether it’s Chuck E. Cheese’s or the many Disney displays, creepy animatronic entertainment was a staple of many of our childhoods. We’re talking MAJOR creep factor, and it’s not hard to think about what would happen if (when?) one of those things goes sentient and starts mauling people.

For those who dug deeper into the Five Nights at Freddy’s lore, you were met with a backstory that involved an old security guard dressing as one of the animatronics luring children to the backroom at the pizza shop and murdering them. This led to people saying that the animatronics looked like "reanimated carcasses," with the story then highlighting how the souls of some of the dead kids inhabiting the animatronics…thus giving you a supernatural sentience that would turn these bad boys on those who they deem bad. You also can’t overlook the idea of the dreaded Boogeyman, a story that is passed down from parent to child, generation to generation, about a being that only comes out at night and is said to literally throw children in a sack to do all kinds of bad to them.

In Five Night’s at Freddy’s 4, this idea is taken to new heights, where the action takes not at a Freddy Fazbear’s Pizza, but in the bedroom of a child who appears to be frightened by everything about Freddy Fazbear and the rest of those animatronics. The Boogeyman is real, and is terrorizing this child for six hours a night. Remember picking up your feet before the monster under your bed grabbed you? Imagine running from door to door with nothing but a flashlight and the ability to shut one of the doors keeping you from true terror.

Another key component in the Five Nights at Freddy’s series is how unique the premise and execution of the games are. With the world of indie gaming blowing up thanks to sites like Steam (and the popularity of jumpscare horror games on YouTube), it can be hard to find a dope game that truly feels fresh and new. For those who dug into Five Nights at Freddy’s, you got that in spades. While the first night in each game tends to get you used to the controls and environment of the game, subsequent nights turn up the heat—you’re having to flip your cameras at lightning speed, then listening for sounds and getting your door closed or flashlight flickered at a moment’s notice before the animatronics get you. Or you’re just having frightening figures like The Puppet jumping out at you out of nowhere. There’s a LOT going on during the later stages of each game (and even more in the unlockable Nightmare nights), and none of it involves the normal hacking and slashing or stealthiness and hiding of many horror games. Nor is there much in the way of gore; a lot of macabre newspaper clippings and stories have come out of the series of games, but you’re never actually seeing murder or any kind of violence, which is where the sounds and sound design are key. The games get eerie based on the noises (or lack of noise) placed in the dark, mysterious environment.

(A lot of that lack of gore and violence might be thanks to Scott Cawthon’s background. Cawthon is a Christian, who made a couple of Christianity-themed games that he called  “financial failures.” In one of his games, the design of a beaver got flamed online, with people saying it looked more like a “scary animatronic,” which in turn sowed the seeds for what has become Five Nights at Freddy’s.)

One thing you can’t rule out when it comes to the Five Nights at Freddy’s popularity is the lore that Cawthon has laced throughout each of the games. As mentioned earlier, the idea of supernatural beings inhabiting the animatronics to seek revenge on those who they feel wronged them has played a huge part in tying each game together, and with Cawthon choosing to not reveal specifics on the timeline of the series has caused an even larger look into what could be going on. One particularly popular theory delves into a shooting at a Chuck E. Cheese in 1993 that crept back into the news in July of 2014. It could be a huge coincidence, or it could be something more. Either way, as the games progressed, there were more cut scenes and interactive mini-games thrown in between each night that were disturbing and depressing, showcases of sad children’s parties and crying souls. Easy Google searches will pull up loads of videos and Wikis that attempt to break down mentioned plot points like the Bite of ‘87 or attempting to place where Five Nights at Freddy’s 4 takes place in the series’ timeline. There’s so much to unpack about the series, and while many fans will theorize, Cawthon isn’t doing any more explaining outside of the games.

Ultimately, the Five Nights at Freddy’s series has done what many wish games or any form of entertainment would do: it has brought something new to the table that people can actually get invested in. The video game landscape is long on “epic” adventures that show off the most tantalizing graphics with hours upon hours of dialogue and adventure; then there’s Five Nights at Freddy’s, the little indie game that could. Replacing those 3D-rendered backgrounds with a mysterious backstory and a host of jumpscares might sound like a recipe of disaster, but it’s turned into gold for Scott Cawthon and the legions of supporters of this creepy franchise. And with a new Halloween update to be released soon, and talk of the next game not being Five Nights at Freddy’s 5, but the rumored 2016 release of the non-horror spin-off RPG FNAF World (where players get to play as the animatronics)—coupled with the upcoming Warner Bros. movie—it looks like the lore of Five Night’s at Freddy’s won’t be going anywhere anytime soon.