Haley resembles a small hedgehog with glowing blue and white quills that appear to be ablaze, a peach colored face and deep blue eyes.
Haley is usually spotted soaring through the skies of more mountainous regions of the Mirror World. Haley simply flies in a straight horizontal path; Haley can move through water, but at a slower speed.
Haley's name and appearance are derived from Halley's Comet.
Its Japanese name is a pun on Halley's Comet and either the Japanese word for needle, 針 (hari), or hedgehog, ハリネズミ/針鼠 (harinezumi).