Gnarl was the chief antagonist of the Buffy episode "Same Time, Same Place".
He was portrayed by Camden Toy.
Gnarl was a type of demon that lived by devouring human skin and was an extremely sadistic, frightening creature, even by demon standards: although a one-shot villain he is notable for being one of the show's more brutal antagonists as he kidnapped a hapless Willow and literally began to eat her alive while taunting her over her fears that her friends would abandon her.
He was described by Dawn erronously as a parasite but in reality he was a parasitod as he killed his victims after prolonged torture - the method Gnarl fed was exceptionally cruel as he would paralyse his victim with a scratch, then proceed to slice off their skin piece by piece and feast: his victims were alive throughout this process as was witnessed when he began to feast on Willow, however Gnarl's existence was put to an end by Buffy after she poked her thumbs into the demon's eye sockets and killed it (presumably via pressure to the brain).
When Gnarl died his paralysing curse faded from his victims, though Willow was forced to use magic to reform the skin she had lost from her ordeal - Buffy helped Willow to do this by lending her some of her Slayer strength, showing that despite Gnarl's previous taunts Willow's friends had not abandoned her after all.