Heidi has black hair tied in an upper ponytail and green eyes. She wears a black T-shirt underneath a crimson jacket, a pair of blue jeans, a black belt and matching black ankle boots with dark green laces and soles. Her voice is similar to Dani Phantom from Danny Phantom.
Heidi is shown to be a very cool and confident kid in her school. She is brave, disciplined, cunning, kind-hearted, selfless, and creative.