Frisk (more formally Punk!Frisk) is the main protagonist/playable character of the Underpunk! AU . They reside in the skeleton household along with sans, Undyne, and Papyrus.
Because Frisk is now a teenager (canonically in AU), they have aged and grown slightly taller. Their hair has changed in length, brown but shorter as well as sporting a spiked collar around their neck. However; they are still adorned with a single stripe across their hoodie: a sign that they have not fully grown out of being considered a child. Frisk also wears what looks to be black jeans and boots.
Frisk is generally "poker-faced" and neutral in terms of physical expression. They do however; express a particular concern for monster's lives that can be interpreted through their narration. On the other hand, Frisk has a more malevolent side to them, as they share a personality with Chara: the first fallen human. This personality isn't yet prominent, but evidence of Chara's pigmentation are apparent (ex. Frisk's flushed cheeks.) on the surface.
Frisk also has a non-verbal disability, that renders them from speaking entirely because of the fall into the Underground since the last reset.
Frisk has the ability of DETERMINATION that is the key to their own willpower and so-called prophecy to escaping the Underground. They also have the ability to gesture and spell out "wingdings" as a form of monster's sign language taught to them by sans, as an alternative way of communication.