With the end of “Coven,” FX’s hit “American Horror Story” has now completed three seasons. The show is billed as an “anthology series,” meaning that each season introduces a new cast of characters, a new time period and a new location.

While those elements may shift every season, one part is consistent: “American Horror Story” is always a wild ride. Combining chills, thrills and even laughs, the show has carved out a niche as the funniest little horror show on TV.

So what makes it work so well? How does a show that literally hits the reset button every season maintain its effectiveness?

For one thing, it’s actually scary. The three seasons (subtitled as “Murder House,” “Asylum” and “Coven”) all tap into and play on common fears.

“Murder House” features the enigmatic Rubber Man, a bevy of ghosts, demon spawn and probably most horrifying of all, a violent home invasion.

“Asylum” has an unsettling setting — a corrupt 1960s mental institution — and also features demonic possession, alien invasion, amputation and a very nasty Santa.

“Coven,” the most whimsical entry in the series, takes a lighter tone, but still showcases the titular horrors. Eye gouging, voodoo, reanimation and twisted body mortification all play a part in the season’s plot.

Some have criticized the everything but the kitchen sink approach that “American Horror Story” often takes in terms of horror, but it’s hard to deny its effect.

By packing in the scares from start to end and by taking them seriously, “American Horror Story” asserts itself as a unique offering in the ever-diversifying TV landscape.

Besides its plethora of scares, “American Horror Story” also works because it’s devilishly funny.

All three seasons exhibit the show’s signature “campy horror” tone, artfully blending the horrifically dark with the darkly comedic.

“Murder House” featured a pack of darkly hilarious ghosts that rolled in and out of the main characters’ lives. “Asylum” featured a demonic nun who didn’t take crap from anybody and a terrific rendition of popular 60s song “The Name Game.”

“Coven” is easily the funniest season so far, featuring scene-stealing performances from Gabourey Sidibe and Emma Roberts. Hilarious but deep turns from Kathy Bates and Angela Bassett as women caught up in the throes of centuries-old racism only added to the comedy of “Coven.”

By combining dark comedy with dark themes, “American Horror Story” is able to keep itself from becoming too much of a downer.

The show’s largest strength, however, is the repertory cast that it’s established over the years.

Jessica Lange, Sarah Paulson, Frances Conroy, Lily Rabe and Evan Peters have appeared in all three seasons, each time playing wildly different characters.

That’s part of the fascination, too: seeing great actors turning in diverse performances. Lily Rabe has played a housewife, possessed nun and a swamp witch over the course of the series, and each time it’s something fresh. Same goes for Lange, Paulson, Peters and Conroy.

The show has also attracted big name guest stars over its run, including performers such as James Cromwell, Stevie Nicks and weirdly enough, Adam Levine.

With its ever-evolving cast and its boundary-pushing scares, “American Horror Story” has made quite a name for itself.

The worst part? Having to wait eight more months for the series’ next installment.