"American Horror Story" is known for its odd humor and grotesque charm, and every once in a while, it even manages to surprise us, albeit with a blood-soaked threesome or demented murder clown, but it's surprising nonetheless. The show's ability to always keep its audience guessing is one of the many reasons fans of "AHS" feverishly try and piece it all together before the season's end.

But even loyal viewers might not know the whole story. How much do you really know about "American Horror Story?" The FX anthology series has always been inspired by real events, but do you know which ones were ripped from the headlines and which were from the twisted mind of Ryan Murphy? Here are 13 unsettling facts about "AHS" that might just keep you up all night:

Hotel Cortez is based off a real hotel in Chicago.

The deadly setting of "American Horror Story: Hotel" is actually inspired by a hotel that was built by H. H. Holmes in Chicago before the world's fair in the late 1800s. Holmes built the hotel with the purpose of murdering his guests and stashing their bodies in the hotel's many trap doors, chutes and hidden passages. It later became known as the Murder Castle. That seems appropriate.

The Chicken Coop Murders were real, too.

The Wineville Chicken Coop Murders was a series of abductions and murders of young boys that occurred in the city of Los Angeles and in Riverside County, California, between 1926 and 1928. Sound familiar? In a harrowing flashback, it was revealed that Ms. Evers' young son was one of the victims.

Sarah Paulson and Evan Peters are the only stars to appear in every season of "American Horror Story."

However, when it comes to individual episode count, Peters has Paulson beat. He's appeared in 64 episodes to date. Paulson has only appeared in 54.

The Murder House is also the Alpha Delta Frat house from "Buffy the Vampire Slayer."

The six bedroom, five bathroom house can be found in Los Angeles. In 2013, it was put on the market for a cool $7.8 million. The home has been a popular film location for TV shows, including "Buffy the Vampire Slayer." You may recognize the Murder House as the Alpha Delta Frat house in "Fear Itself," an episode from Season 4 of "Buffy."

Evan Peters covered himself in lubricant to get into his Rubber Man costume.

TBH, that makes a lot of sense. That Rubber Man costume was skin tight!

The guy who created the show's unsettling opening credits also created "The Walking Dead" opener.

The opening credits are an important part of "American Horror Story," since, aside from being skin-crawlingly unsettling, they also contain clues and riddles about what's going to happen throughout the season. It turns out that the man responsible for the show's jittery trademark opener is Kyle Cooper, the same genius in charge of creating the opening credits for AMC's "The Walking Dead."

Edward Mordrake was a fictional character long before "Freak Show."

The tragic tale of Edward Mordrake was created by science fiction writer Charles Lotin Hildreth in 1895. The writer claimed that Mordake, heir to an English peerage, had an extra face on the back of his head, one that could neither eat nor speak out loud but was seen to "smile and sneer while Mordake was weeping." Yeah... no thanks.

Real-life clowns are not fans of Twisty.

Professional clowns, who make a living from their appearances, thought the "Freak Show" murder clown contributed to "clown fear," and were 100 percent not down with Twisty. To be fair, Twisty doesn't exactly make me want to run into a clown anytime soon. Then again, neither did Pennywise.

The murdered cheerleader played Evan Peters' girlfriend on "One Tree Hill."

Throughout "Murder House," Kyle is constantly confronted by the ghosts of several students he murdered, including a brunette cheerleader played by Ashley Rickards. On "One Tree Hill," Peters and Rickards played Tree Hill OTP Jack and Sam.

Evan Peters flashed his co-stars during a shower scene.

While getting hosed down during a scene in "Asylum," Peters accidentally flashed Sarah Paulson and Jessica Lange. We feel like Paulson and Lange were pretty chill about it.

Zachary Quinto loved to play the banjo on set.

Who knew Zachary Quinto was such a fanatical banjo aficionado? While on the set of "Asylum," Quinto would perform for the cast and crew between takes. "I play my banjo on set a lot because it sort of lightens up the mood," the actor said. "At first I was a little bit nervous about doing that and then people were like, 'Thank you for doing that. It makes it so much easier to work.'"

Every scene with Bette and Dot took nearly 15 hours to shoot.

Paulson's scenes as Bette and Dot took a combination of visual effects and puppeteering to achieve the appearance of two heads. Luckily for Paulson, Hypodermic Sally has only one head in "Hotel."

Every season of "American Horror Story" is connected... or so we've been told.

Last year, Ryan Murphy revealed that every season of "AHS" is connected in some way. Lily Rabe's return as Sister Mary Eunice in "Freak Show" was the first real clue, followed by the return of the Murder House -- and Dr. Charles Montgomery -- in "Hotel." While nothing has been officially connected to "Coven," the series' wacky third installment, the fact that Madison Montgomery (Emma Roberts) and shares the same last name as the Murder House's original owner has not gone unnoticed to fans.