The Sphinx likely had a cat head at first.

Why do many Egyptian Gods have mixed human & animal features? Long ago there were 2 kingdoms now called Upper Egypt & Lower Egypt. Each had its own pantheon of Gods. One represented the forces of nature with humanoid powers;; the other had sentient animal deities. After the kingdoms united into the country now known as Egypt, their cultures were blended, & Gods who served the same functions merged into the half & half forms seen today.