"Hey.. uhh... I've heard there is something roaming the place.. I think it's a... fox endoskeleton..? It definitely doesn't belong to uh.. Mangle.. or Foxy... but it's... something..." Phone Guy talking about Spring in the night 3 phone call, in FNAF2.
Spring looks like a fox endoskeleton with yellow eyes. She is missing one ear, in which there are wires coming out of it. She is also missing one of her hands.
MORE TO BE ADDED
THIS IS A WORK IN PROGRESS