Here's why:
* Marsupials are mammals that give birth to relatively undeveloped young which then complete their development in a pouch. Hedgehogs do not have pouches.
* Rodents are characterized by having two large, continuously growing incisor teeth in both the upper and lower jaw. While hedgehogs have sharp incisors, they do not grow continuously.
Hedgehogs are unique animals with their own distinct evolutionary history and characteristics.