“Cabin in the Woods” is the kind of movie best watched spoiler-free. Not because there are shocking twists à la M. Night Shyamalan, but because the film unfolds one piece at a time, building slowly on the amount of information the audience knows. By the time the complete picture is clear, horror movie clichés have been flipped, tropes acknowledged and genre muddled. What at first seems stereotyped and rote becomes a meta-conversation on the phenomenon of paying 10 bucks to watch teenagers get covered in blood on the big screen.

So for spoiler-phobes, let’s just say this. It’s a funny, original movie where about 75 percent of the way through, there’s a killer unicorn. Go see it.

For everyone else, you’ve been warned. It’s near impossible to discuss this movie without giving anything away, so I’m not even going to try.

“Cabin” follows five college students looking to get off the map for a weekend. Two hot girls, two jocks and a stoner load up the RV and split for the titular cabin, which is located in the titular woods. Said cabin is lushly decorated with grotesque taxidermies and violent paintings. During the group’s drunken shenanigans, they inadvertently summon an unspeakable evil with a lust for blood – a fate rather bluntly alluded to earlier on by a requisite eerie backwoods gas station attendant.

If that was all “Cabin in the Woods” amounted to, it would be called “Evil Dead,” and it would have been released in 1981 – that, or one of its many creative offspring, including 2002’s “Cabin Fever” and 2003’s “Wrong Turn.” There’s some “Texas Chainsaw Massacre” in there, too.

But “Cabin” was co-written by Joss Whedon, the man who made vampires afraid of petite, blond, high-school girls with sassy catch phrases. While the dialogue in “Cabin” avoids the “Buffy Speak” Whedon is known for – which originates from his earlier project, “Buffy the Vampire Slayer” –  it lavishes on the genre-bending and self-referencing.

The second set of main characters in “Cabin” is comprised of two jaded government officials, played by Bradley Whitford (“The West Wing”) and Richard Jenkins (“Six Feet Under”). The pair sits in a control room, controlling the events transpiring at the cabin and watching the bloodbath on television monitors. They are part of an international government project whose purpose is to appease ancient gods through human suffering and sacrifice. Thus, the movie is not about what goes bump in the night at the cabin in the woods – it’s about who’s watching.

Any movie that begins with Whitford walking briskly down a hallway, discussing serious government business is setting itself up to be referential, and “Cabin” mostly pays off in that respect. From the cabin itself looking like a replica of the cabin from “Evil Dead” and the mention of an “angry molesting tree” as a possible fate for the protagonists, to the cameo of the little girls from “The Shining” and a man who looks suspiciously like Pinhead’s cousin, “Cabin” pays loving homage to horror movies as much as it parodies and comments on them.

The movie closest in relation to “Cabin in the Woods” is 1996’s “Scream,” arguably the first genre-savvy horror movie. The stoner character in “Cabin,” Marty (Fran Kranz), is very similar to Jamie Kennedy’s character in “Scream.” They understand the machinations of the world they inhabit and announce in-universe what audiences have been screaming at the screen for decades: Don’t split up! Don’t go out into the woods! Don’t have sex! Don’t read the ancient Latin inscription out loud!

While there were horror-comedy hybrids before “Scream,” and tongue-in-cheek horror has been something of a staple ever since – nothing else has reached the same level of meta-genre until “Cabin.” But “Cabin” doesn’t feel like “Scream” rehashed, due mostly to the level of brilliant absurdity in the second half of the film. If “Cabin” was just zombies or just ghosts or just monsters, it might have fallen flat. But no, in this cabin in the woods, you get anything and everything that’s ever haunted a nightmare, right down to the killer unicorn.

While it takes a few minutes to get going, “Cabin in the Woods” ends up being laugh-out-loud funny. Whitford and Jenkins are easily the most hilarious part of this movie, bantering back and forth, mocking the suffering teenagers and trying to ignore the implications of their work. Kranz gets some laughs as the resourceful burnout as well. The film’s excessive use of blood for comedy’s sake – which can sometimes just be excessive for the sake of excess, to its detriment – usually works well, especially when the blood is being spewed from a merman’s blowhole.

The ending has trouble standing up to the epic mania of the third act. The government officials reference the Big Bad as “ancient ones” a few times, giving false hope that Cthulu might make an appearance before credits rolled.

But most wasted is a casting gag in the final scene. A certain beloved science-fiction star shows up as the evil program director, but ends up only filling in plot holes before being unceremoniously killed off. This would not have been so bad, had her death been caused by something more, shall we say, extraterrestrial. If you’re going to make a bunch of movie references, you might as well go all the way. Spoiler alert.

Victoria Knobloch can be reached at [email protected].