The Furbie-esque Nubbins in Sanctuary are a variant of this — they're only dangerous in large groups and when being directly attacked, but their extremely high reproductive rate and lack of predators outside their natural environment make them potentially highly destructive to the ecosystem. Unfortunately, they're a Hive Mind far brighter than they seem, and are more than willing to sacrifice individual lives to escape and spread. Loook what happens to the large, vicious wolf-like abnormal the team sends after the nubbins. Look at the bones, indeed.
In an episode of Honey, I Shrunk the Kids called "Honey, the Bunny Bit It", Nick Szalinski revives the school mascot à la Frankenstein, and chaos ensues as it runs amok.
An Americas Funniest Home Videos episode features a rabbit fighting a snake. The rabbit kicks the snake's proverbial ass, forcing the reptile to retreat up a low-hanging tree, despite the rabbit attempting to yank the snake down for more.
Doctor Who: The Cybermats in "The Wheel in Space". At least one of their victim actually begs them gently to come closer because he isn't going to hurt them before they do, and hurt him.
Kamen Rider Drive: Kamen Rider Mach's Signal Danger power allows him to summon a Conspicuous CG creature that looks like a mix between a bullet and a shark; while this might sound scary, it's only about a foot long and has a cute nervous expression on its face. And then it plays the trope straight by growing ten times its normal size and mauling Monsters of the Week.