Focusing on its appearance:
* As awkward as a duck with a beaver tail.
* As fuzzy as a teddy bear with a duck bill.
* As strange as a cross between a duck and an otter.
* As cute as a cartoon creature with a poisonous spur.
* As fascinating as a living paradox.
Focusing on its abilities:
* As venomous as a snake with a webbed foot.
* As skilled at digging as a mole with a duck bill.
* As adept at swimming as a seal with a beaver tail.
* As mysterious as a creature from a fantasy novel.
* As perplexing as a riddle wrapped in an enigma.
Remember to choose the simile that best fits the context of your writing.