Adorable Abomination

Let's face it. We all love Cute things. Some like Cute for Nostalgia. Some like cute for... Perverted reasons. There are even people who think ugly things are cute! But sometimes Cute overlaps with Terror. Bonus Points if it's something from an animated work. Can overlap with Killer Rabbit.

Compare Grotesque Cute. Not to be confused with Cute Is Evil, but it can overlap.

Anime & Manga

 * Higurashi. Practically everyone in it is cute, but sooner or later they all end up killing one another.
 * Elfen Lied. There was a scene where a little girl was in a house, and two firefighters came to get her, but she kills them both on the spot.
 * from Madoka Magica. Given that he's actually a Starfish Alien with Blue and Orange Morality, and that at one point he, yeah, he qualifies.
 * Kamineko from Azumanga Daioh. Sure, he looks cute, but he has a grin that resembles a bear trap and a bite to match. At Times they'll even play what sounds like the theme from Jaws when he appears!
 * Not even Yu-Gi-Oh! is safe. Behold (Cue Drum Roll)... Kureboh!
 * Hazuki from Moon Phase. A cute little girl right? But when the moon comes out and she goes into Luna mode... bad things happen.
 * Kirby, at least according to Kirby of the Stars. Also, Gooey from the games, who is a piece of Dark Matter who broke off, turned good, and became Kirby's friend.

Films -- Animation

 * The Stitchpunks from 9|Nine.
 * Besides Plushes, some of the WALL-E items are kinda creepy.
 * Toothless from the How to Train Your Dragon movie can switch from Cute to Fierce by changing his eyes.

Live-Action TV

 * The Cybermat from Doctor Who. It's a little silver thing that scoots around the floor. And then you see the razor-sharp teeth.

Tabletop Games

 * Pokethulhu and Mortasheen display two very different ways to apply this to the Mons genre. The former is full of cute, adorable creatures that love to eat souls, while the latter is full of frightening, hideous monsters that become friendly and loyal when tamed.

Videogames

 * Some species of Heartless and Unversed from Kingdom Hearts fall into this trope. All are Eldritch Abominations; some happen to be adorable.

Webcomics

 * Erma, in Erma.

Web Original

 * Whateley Universe example: Josie Gilman's cute little black kittycat. It loves to be hugged, it loves to be fed, it... oh my god it's an Eldritch Abomination with a huge gaping maw!!!
 * The cuddly stuffed cabbit Generator made for Tennyo should count too. Especially when the claws and fangs pop out.

Western Animation

 * This is what the people in charge of Heloise's personallity in Jimmy Two-Shoes seem to want to protraied as. It doesn't work