"Many a Muggle child has been accused of vandalism when an offended Knarl was the real culprit."
-- Newt Scamander (FB)
A knarl is very similar to a hedgehog, except for behavioral differences: the distrustful knarl takes offense if food is left out, and will take revenge by wreaking havoc on garden plants and ornaments (FB).
- Part of the O.W.L. test in Care of Magical Creatures involved knowing how to distinguish between a Knarl and a hedgeghog (OP31).
- Knarl quills are used in the Laughing Potion (BoP).
From the Web
"Knarl" from Harry Potter Wiki