Fastener is a peculiar demon character from the anime series "Panty & Stocking with Garterbelt." He serves as Scanty and Kneesocks' pet, taking on the appearance of a red, devilish counterpart to Brief's pet Chuck. Fastener is known for his mischievous and often chaotic antics, adding comedic and unpredictable elements to the storyline. Though he does not play a central role, his presence contributes to the chaos and humor that define the series, often clashing with Chuck in humorous, over-the-top encounters.