You can't have an adventure without a hero and you can't have a hero without a villain. Animators working on children's entertainment know that. Sometimes they get carried away a bit and that's when the creepiest cartoon characters get created.

These animated films may begin like any other, but as their heroes battle the overwhelming odds against them, they turn into some of the scariest cartoons for children. That doesn't mean they're bad, though: it's that very struggle against evil and injustice that makes these stories dramatic and memorable.

In our list of the 13 Scariest Cartoon Characters Of All Time, we're taking a look at some of more family-friendly cartoons that nevertheless managed to sneak in some darkness and danger.

13. Venom - Spider-Man (1994)

Thanks to Venom, we know what an alien-human hybrid looks like. Similar to H. R. Giger's most famous creation, Venom possesses a huge teeth-filled maw with a lower jaw that he can unhinge like a snake. Add to this a Hulk-sized body and cover it with a peculiar black goo that can change its shape into spikes and tentacles. What you get is some good old-fashioned nightmare fuel!

The character of Venom originated as an idea by a Spider-Man fan to give Peter Parker an improved costume with cooler colors. Marvel bought the idea, which was then developed by the comic book illustrator Mike Zeck. Spider-Man's new costume was introduced in comic books in 1984 as a sentient symbiotic creature that granted Peter Parker new powers, but also tried to impose its will upon him. By 1988, the alien symbiote bonded itself to a new bad guy, Eddie Brock, and called itself Venom. Venom made its first TV appearance in the 1994 Spider-Man cartoon where he was voiced by Hank Azaria.

12. Mumm-Ra - ThunderCats (1985)

Pale, wizened and draped in a tattered cloak, Mumm-Ra (voiced by Earl Hammond) lurks from within the Black Pyramid among the ruins of an ancient civilization. That's pretty creepy for a Saturday morning cartoon villain, but the thing about Mumm-Ra is... that's his casual, everyday form. When he gets really angry, he calls upon the Ancient Spirits of Evil to grant him the form of Mumm-Ra the Ever-Living, who looks like a zombie on steroids. It's a silly concept and yet, Mumm-Ra manages to pull it off.

But here's the most unsettling thing about Mumm-Ra: he can't be killed. The heroic ThunderCats, led by Lion-O (Larry Kenney), defeat Mumm-Ra again and again, only to have him attack them again once he regenerates. Produced by Rankin/Bass Productions, ThunderCats debuted in 1985 and aired for four seasons in syndication. The cartoon was revived in 2011 but got cancelled after a single season.

11. Lawrence Limburger - Biker Mice from Mars (1993)

Biker Mice From Mars was a fairly popular Saturday morning cartoon series that originally aired in syndication in mid-1990s. It follows a trio of alien humanoid mice as they battle the schemes of evil Plutarkians, aliens who ecologically devastated their own planet, all but exterminated the Martian mice, and are now covertly plundering the natural resources of our world.

The main villain in Biker Mice From Mars is Lawrence Limburger, who is seemingly just a corporate mogul dressed in a purple pinstripe suit. Except that Limburger is actually an alien from Plutark who occasionally peels off his human skin revealing a bloated fish-like creature beneath. Once you see that, it's hard to stop thinking how that fake skin is stretched to the breaking point under the pressure of a corpulent monstrosity underneath. The only way to make such a creature creepier would be to see it in a live-action movie.

10. Chernabog - Fantasia (1940)

The first of the several Disney villains on this list is a dark deity from Slavic mythology known as Chernabog. He appears in the final segment of the 1940 animated film Fantasia as a colossal demonic being looming over the lesser evil spirits, accompanied by the Night on Bald Mountain, a classical composition by the Russian composer Modest Mussorgsky. As dawn approaches, Chernabog runs away and Schubert's Ave Maria begins to play... But nobody really remembers that part of the movie because Chernabog is so much cooler than the ghostly monks that follow.

Walt Disney's Fantasia began as a short segment featuring Mickey Mouse accompanied by the orchestral piece The Sorcerer's Apprentice by Paul Dukas. As the segment itself was quite expensive, yet too short to be released in cinemas by itself, it was soon accompanied by seven other animated segments inspired by the classical works of Bach, Beethoven, Stravinsky, Tchaikovsky and others. Although financially unsuccessful upon its release, Fantasia earned some $70 million throughout the next few decades.

9. Grigori Rasputin - Anastasia (1997)

Since the historical mad monk Grigori Rasputin was pretty much a cartoon villain brought to life, it made perfect sense for director and producer Don Bluth to turn him into one for his animated musical epic Anastasia. Killed early in the movie, Rasputin (voiced by Christopher Lloyd) nevertheless survives due to his dark magical powers. Yet, his body just keeps falling apart, to a gruesome and ridiculous effect. Rasputin places a curse on a Russian imperial family who all die in the Russian Revolution, but for the young princess Anastasia (Kirsten Dunst) who loses her memory.

Anastasia was inspired by the 1956 movie starring Ingrid Bergman and Yul Brynner that was in turn based on a real-life case of Anna Anderson who became famous in the 1920s for her claim that she was really the only surviving child of the last Russian emperor. Produced by Fox Animation Studios, Anastasia earned almost $140 million in cinemas, becoming by far the most successful animated film directed by the former Disney animator Don Bluth.

8. Professor Ratigan - The Great Mouse Detective (1986)

In a hidden world of the Victorian mice, Professor Ratigan (voiced by the horror movie legend Vincent Price) is a rat. Dressed in a dapper suit, Ratigan is nevertheless a hulking monstrosity compared to others around him, not unlike Mr. Hyde in Alan Moore and Kevin O'Neill's graphic novel The League of Extraordinary Gentlemen. A sadistic thug hiding under a thin veneer of civility, Ratigan is quick to throw henchmen to his pet cat, Felicia as snack food.

In the early 1980s, Disney tried to appeal to older children with several darker and more mature animated films. One of them was The Great Mouse Detective. Released in 1986, it was based on a series of children's novels by Eve Titus about the adventures of the brilliant mouse detective Basil of Baker Street (voiced in the film by Barrie Ingham) who lives and works out of a basement in Sherlock Holmes' home. The box office success of The Great Mouse Detective may just have saved Disney's animation department, as it arrived at just the right time to show its commercial viability to the new management.

7. Hexxus - FernGully: The Last Rainforest (1992)

Hexxus (voiced by the legendary Tim Curry) is an evil spirit imprisoned in a tree by the fairies of the FernGully rainforest. When one day lumberjacks start cutting down trees, they not only antagonize the fairies led by Crysta (Samantha Mathis) but accidentally release Hexxus, who assumes the form of the pollution itself. FernGully: The Last Rainforest deliberately uses the haunting images of ecological disasters and personifies them into a seemingly unstoppable villain, Hexxus, who can't be truly destroyed but only imprisoned.

Directed by Bill Kroyer, FernGully: The Last Rainforest was an animated movie made as a joined Australian-American co-production. It premiered in 1992 and soon became a box office success that received mostly positive reviews. It marked the first ever voice acting role for Robin Williams, who would go on to provide the voice for Genie in Disney's Aladdin, released that same year.

6. Jenner and Dragon - The Secret of NIMH (1982)

There are monsters everywhere when you're just a mouse. Mrs. Brisby (voiced by Elizabeth Hartman) is a tiny field mouse trying to save her sick son from pneumonia. On her quest, she encounters a host of scary creatures, both benevolent and otherwise. There's the Great Owl (John Carradine) with his glowing yellow eyes and ruthless rat named Jenner (Paul Shenar). But possibly the scariest part of the film comes when Mrs. Brisby has to creep alone into a human household and put sleeping powder into the food of a fierce tomcat, Dragon, who already killed her husband.

American animator Don Bluth began his career working for Disney. In 1979 he started his own studio with a group of fellow Disney animators who weren't happy about the direction the animation giant was heading in. Their first project was based on the children's novel Mrs. Frisby and the Rats of NIMH by Robert C. O'Brien. Although The Secret of NIMH was well-received by audiences and critics alike, Bluth's studio was nevertheless forced to file for bankruptcy soon after its release.

5. The Horned King - The Black Cauldron (1985)

The Horned King is what Skeletor wants to become when he grows up. With a skull-like face and an emancipated body wrapped in a long cloak, the Horned King (voiced by John Hurt) is a feared ruler of a derelict castle deep within the swamps in the mythical land of Prydain. He controls a small army of thugs and monsters, but is far more ambitious than that. The Horned King wants to get his claws on the magical Black Cauldron and use it to create an army of undead warriors. And he would have gotten away with it, if it wasn't for that meddling kid Taran (Grant Bardsley)!

Made by Disney, The Black Cauldron was based on the first two books in The Chronicles of Prydain series by Lloyd Alexander. The film was scheduled for the 1984 release, but the children in the test audience reacted badly to the scenes of carnage at the film's finale, so The Black Cauldron was re-cut. Finally released in 1985, it nevertheless failed at the box office and received mixed reviews.

4. Him - The Powerpuff Girls (1998)

You don't often get to see Satan as the cross-dressing villain of a kid-oriented cartoon. Him may not look especially threatening - aside from those pincer hands, yikes! - but when voice actor Tom Kane and whatever mad genius of a sound designer Cartoon Network used work their magic, Him is creepy as hell. His lazy voice sounds like a very essence of corruption, always echoing as if originating from the bottom of a rancid well. But there's madness and fury underneath that can boil over at any moment.

What also makes Him deeply unsettling is that, unlike other villains in The Powerpuff Girls, he doesn't fight the show's superheroes for the sake of money, power or revenge. Instead, he uses manipulation, corruption and psychological torture to break them for the sheer evil of it. And if that isn't creepy, then nothing is!

3. Judge Doom - Who Framed Roger Rabbit (1988)

Just because a film features cartoon characters doesn't mean it's 100% kid-friendly. And no kid who ever saw Robert Zemeckis' 1988 film Who Framed Roger Rabbit will easily forget Judge Doom (Christopher Lloyd). Based on a novel by Gary K. Wolf, this noir parody is set in a world where human beings and animated characters uneasily coexist. Eddie Valiant (Bob Hoskins) is down-on-his-luck private detective working on a murder case involving a famous cartoon star Roger Rabbit (voiced by Charles Fleischer) and his voluptuous wife Jessica (voiced by Kathleen Turner).

Judge Doom is a sadistic official covering all the cases involving cartoon characters. Doom is in finally revealed to be a cartoon character himself wearing fake skin as a costume. With his shrill voice and demonically-bulging eyes, Judge Doom is frightening and his death proves equally gruesome. When flattening him with a steam-roller proves to be ineffective, Doom gets dissolved by a toxic chemical mix of his own invention. Pleasant dreams, kids.

2. General Woundwort - Watership Down (1978)

Watership Down follows a group of cute, fluffy rabbits led by brothers Fiver (Richard Briers) and Hazel (voiced by John Hurt) on a quest to find a new warren before their tribe gets brutally slaughtered by humans. After barely surviving their trip, the heroic rabbits finally arrive at Watership Down only to face their greatest threat: a nearby warren that is led by General Woundwort (Harry Andrews), a thuggish, cunning and utterly heartless despot.

Released in 1978, Watership Down was based on a 1972 novel by Richard Adams that was rejected by six publishers before finally being published. Despite its seemingly silly premise, novel became a hit because of its mature exploration of themes such as courage, faith, self-sacrifice and sense of community. The film adaptation of Watership Down was a box office success and received mostly positive reviews.

1. Orcs and Nazgûl - The Lord of the Rings (1978)

In Ralph Bakshi's 1978 animated adaptation of Lord of the Rings, Tolkien's monsters are truly a stuff of nightmares. Bakshi's film was made using the live-action footage which was then rotoscoped to make it appear as if animated. The result is a somewhat unsettling hybrid between the two mediums.... and that's before the Orcs and Nazgûl appear. When they do, they're not even creatures, but more like black holes in a cartoon landscape, horrendous intruders from some alternate dimension.

Ralph Bakshi is an American film director who first rose to prominence in 1972 with his animated film Fritz the Cat, based on the cult underground comic by R. Crumb. Bakshi proceeded to make a series of animated films like Wizards (1977) and Fire and Ice (1983) that were more adult-oriented alternatives to mainstream animation. Unlike the Peter Jackon's version of The Lord of the Rings though, Bakshi's adaptation wasn't successful enough to warrant a sequel.

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What were your most memorable scary cartoons you saw as kids. Share them with the others in the comments below?