If you're going to make a monster movie, be sure you don't skimp out on the most important detail: the monster. So many movies in this sub-genre of horror and science fiction fail because the filmmakers underestimate or neglect their creature. Sometimes these slapdash-looking beasts are just the products of miscommunication or a lack of creativity.

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No matter the reason, though, we the viewers cannot help but feel disappointed when the monsters end up looking second-rate. Especially when we are anticipating that moment when we finally get to see the creatures in action. So, looking back through the history of film, here are ten of the most disappointing horror movie monster reveals ever.

Boogeyman (2005)

Boogeyman Barry Watson (2005)

Although Boogeyman was a modest hit for Ghost House Pictures and Sony, the film was a critical failure. This PG-13-rated tale of something that goes bump in the night was panned through and through. Lead actors Barry Watson and Emily Deschanel were complimented for their performances, but even they weren't enough to change the course of this sinking ship.

One of the film's major detractors was the lack of the titular villain. Yet when we finally do see the Boogeyman, we can understand why they kept him under wraps for so long.

Rawhead Rex (1986)

Clive Barker is known for writing some of the most macabre horror stories in existence. After all, he gave us Hellraiser. His monster feature Rawhead Rex, however, suffered under the fact that its namesake was so utterly goofy-looking.

Barker wasn't to blame; the pagan god failed to muster up more than laughs because of the stiff suit. The movie's low budget also hindered any chance of intricate animatronics that would have made Rex look more, well, animated. Clive Barker has been open about his disappointment with the film, and director George Pavlou has expressed interest in a remake.

The Boogens (1981)

Eighties monster movies are the best, right? There's just something about that era that gives horror and sci-fi fans the feels. But, in all honesty, not everything looked as good as the alien in John Carpenter's The Thing. Case in point is the obscure 1981 creature feature The Boogens.

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Although the film has a rather satisfactory rating on IMDb, it's not because of the creature designs. The monsters in the movie turned out to be tentacled, fanged turtles trapped beneath a silver mine. If you can get past the hard shell, The Boogens is an otherwise amusing B-movie.

Jack-O (1995)

If cheesy cinema is your bread and butter, then 1990s straight-to-video horror is for you. In 1995, slasher fans were treated to one of the most ineptly made movies in some time. Jack-O concerns a sleepy hamlet being terrorized by a pumpkin-headed demon originally conjured by an ancient warlock. Steve Latshaw was the mind behind other shoestring stinkers like Dark Universe and Biohazard: The Alien Force.

The antagonist in Jack-O wouldn't scare anyone on Halloween night. His bulbous gourd of a head and his pinned mobility make for a sluggish, sad-looking villain.

Stephen King's Sleepwalkers (1992)

Sleepwalkers was Stephen King's first movie where the script wasn't based on a pre-existing work. The 1992 movie follows the two survivors of a vampiric, cat-like humanoid race as they seek sustenance. And what they feed on is female human virgins.

These beasts can shapeshift, cast illusions, move objects with their minds, and siphon others' energy. What they can't do, however, is not look like some kind of overgrown, hairless cats with a permanent sneer across their snouts. The CGI transformations are entertaining if not dubious. It's the cat vampires' final form, though, that sends us into a fit of giggles.

Humongous (1982)

Paul Lynch's 1980 movie Prom Night is considered a slasher staple. His horror followup Humongous, however, is not. This lesser-seen effort is about a group of friends going sailing, then crashing their boat on a small island. They are eventually picked off, one by one, by an unseen maniac. When we finally do see the killer, we completely understand why he remained in the shadows.

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Before Humongous hit Blu-ray, the few fans of this run-of-the-mill slasher were stuck with copies where you could hardly see anything. The black colors were so stark, it was virtually impossible to catch a glimpse of the villain. In the high-definition release, viewers now know what he looks like. And they are not impressed.

Deadly Eyes (1982)

Based on James Herbert's novel The Rats, Deadly Eyes has a city under siege by larger than normal, bloodthirsty rats. This movie was one of many creature features made in Jaws' wake. This era of horror was rife with movies reflecting growing concerns about the environment. Case in point, the rats in Deadly Eyes grew so big because they consumed contaminated grains.

There are a number of other killer rodent movies out there, but only Deadly Eyes dressed dachshunds up, as far we can tell. It's plain to see that these rats are just wiener dogs incognito. Unfortunately, this "nature's revenge" movie suffered a real life casualty as one of the dachshunds died during filming.

There's Something Out There! (1991)

Ten years after the slasher sendup Student Bodies and five years before Scream changed nineties pop culture, the 1991 horror comedy There's Something Out There! poked fun at horror tropes in the most risible way. Sadly, though, not a lot of people saw There's Something Out There! back in 1991.

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It went unnoticed even by horror fans until years later. As tongue-in-cheek and self-aware as There's Something Out There! is, one cannot help but raise an eyebrow at its killer of choice. The movie, for some reason, opted for an alien tadpole as opposed to a real person. It deducts a point or two from the overall enjoyability, but not enough where you should skip the movie altogether.

Cursed (2005)

Cursed (2005)

The late director and horror icon Wes Craven was undoubtedly unhappy with how his film Cursed turned out. Oh sure, his fans are very forgiving, and many of them like this werewolf flick. That doesn't mean Cursed is absolved from its flaws.

Cursed was in production purgatory for several years. The script finished in 2000, but the film was released in 2005 after being reshot and postponed since 2003. It was so tardy to the party that its own pop culture references — Craig Kilborn appears as part of The Late Late Show, but he stepped down as host in real life by 2004 —were already outdated. What's worse is replacing the practically rendered werewolves with dodgy CGI.

Up from the Depths (1979)

Steven Spielberg probably did not expect Jaws to be so innovative. His movie not only changed creature features, but it generated a surplus of copycats that are better left at sea. One of the absolute worst is Up from the Depths, a 1979 shark flick filmed in the Philippines.

Director Charles B. Griffith had an unpleasant time making the movie. He intended to make an action film, but the creature designers in the Philippines had constructed a comical-looking fish prop instead. Griffith didn't want to upset the designers, so he made a comedy instead. And that he did.

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