There was an episode of Happy Days where the Fonz, who had always been effortlessly cool, got on some water skis and jumped over a shark. Some viewers felt that act was trying so hard to make Fonzie look cool that it actually just looked desperate - and thus the phrase "jumping the shark" was born.
Here's the thing about jumping the shark: sure, jumping one shark might be trying too hard - but jumping twelve sharks goes back around and becomes cool again. Actually, lining up a dozen sharks goes beyond coolness. At that point you are dealing with such total desperation that it's fascinating; you're dealing with such commitment it's compelling; you're dealing with a trainwreck of such large proportions that it transcends the need to be merely cool and becomes it's own unique chance to rubberneck.
Horns is a movie that jumps twelve sharks.
When Horns opens, a young man named Ig Perish - (we're already at shark number one and I haven't even used a verb yet) - is in legal trouble because everyone assumes he murdered his girlfriend Merrin by bludgeoning her to death with a rock. Ig is really indignant about these accusations, because he's loved Merrin since the first time he saw her - which, incidentally, was in church as she tried to communicate with him in Morse code by reflecting bursts of light off of her cross necklace. (I know that's weird, but is that weird enough to earn a full shark? Or is that just a dolphin?) Ig knows he didn't kill her at the foot of the tree house they used as a fuck palace but nobody believes him, and the stress of the accusations is really getting to him.
So a desperate Ig gets drunk and has a one night stand with a bartender who has had a crush on him since they were children. (Everyone in this movie seems to be permanently imprinted on the person they loved when they were 12, and since it only worked out for Ig and Merrin all of their friends seems pretty bummed about their lot in life. It's an out of left field touch, and it makes no sense in the modern world of internet dating and leaving your hometown to go to college - shark #2.5.) When he wakes up in the bartender's bed Ig discovers that he has grown horns. And not just any horns - horns with magic truth telling powers. Anyone who is near Ig has to compulsively divulge their deepest secrets to him.
As far as movie premises go, that's pretty sharky.
Now here is where Horns earns SO MANY of it's sharks: it has absolutely no idea how to portray all of those secrets. Some of the reveals are meant to be broadly funny - two of the cops that are hassling Ig turn out to be secretly gay for each other, which the film seems to think is hilarious. Some of them are meant to be funny but are fucked up in context - a waitress tells Ig that the reason why she lied to the cops about seeing him drag Merrin to his car was because she wants to be on TV and maybe his tabloid murder case will help her get a reality TV show. Some of them are just straight fucked up - Ig's parents both regret being related to him now that he's been accused of such a heinous crime. The tonal whiplash between "these people's secrets are generically wacky" and "these people's secrets are shockingly dark" is worth at least three sharks, maybe three and a half.
By the middle of the movie - when it's revealed that Ig can summon and talk to snakes (PARSELTONGUE WHHHHAAAT!) - the film has completely lost it's goddamned mind. It's trying to be a parable about honesty; a coming of age story about two young lovers that's meant to be sweet; a coming of age story about two young lovers that's meant to be sexy; a murder mystery about a dead teenager; a thriller about a man with occult powers; and a comedy about how much wackiness would ensue if we couldn't lie anymore. In many ways it feels like an exquisite corpse, as if the script had been handed off to a bunch of different writers who could only read the scene immediately before them, so they knew the story involved a guy with horns, but they had no idea who he was as a person or what world he lived in.
Actually, a better metaphor might be this: Horns is like Twin Peaks - except instead of spreading out all the depravity, surreal comedy and police work over a full season of TV, it was crammed into one movie. (Horns actually even looks like Twin Peaks, since it is also set in a Pacific Northwest logging town.) That compression makes Horns feel manic where Twin Peaks often felt indulgent. Because it wants to cram so many disparate ideas into such a small space, Horns creates a "what the hell is going to happen next?" feeling that isn't particularly subtle, but is enjoyable if you're in the right mindset.
If Horns had it's one idea about a guy with magic truth telling appendages, it would be fairly boring - it's a pretty literal metaphor, and it would get old pretty quickly. Fortunately, Horns has a lot of ideas, and it has too much on it's mind to stick to one dumb metaphor. As a result, it shoves flaming angels, suicide by psilocybin, and gay cops doing each other in a squad car into one non-stop mess. At first it seems like the wrong call - you see this movie go over one shark and you think "well, boo", and then the second shark is so dispiriting you don't even bother to boo, you just roll your eyes - but eventually it's power becomes clear. Somewhere around the tenth shark you'll start to chant "more sharks! more sharks!" And then Horns will give you more sharks. In the world of Horns there are always more sharks.