Shantak-kun is a female shantak, a Cthulhu Mythos creature resembling a bird with a horse's head and bat-like wings. She serves as the primary pet and loyal companion to Nyaruko, the series protagonist. Capable of dramatic size alteration, Shantak-kun shifts from multi-story building dimensions down to rabbit-like proportions. She also transforms into functional vehicles, notably a spaceship Nyaruko employed to journey to Earth.

Functioning practically in Nyaruko’s activities, Shantak-kun assists in transportation and missions. Her eggs are a highly prized, expensive delicacy across space, though consistently refused by the human Mahiro Yasaka. She exhibits intelligence through telepathic communication with Nyaruko and others, alongside unexpected physical strength like lifting heavy objects or carrying individuals through the air.

Across all official media—television series, OVAs, and light novels—Shantak-kun maintains a consistent role as Nyaruko’s supportive pet without significant narrative development or backstory expansion. Her abilities and relationship with Nyaruko remain stable, primarily functioning as a versatile tool for transportation or comedic effect. No substantive evolution occurs in her character arc, background, or interactions beyond this established supportive capacity.