[Shadow's original story is depressing, so I did my own thing]

Your uncle, Gerald Robotnik, made a little black and red hedgehog for your illness, known as Neuro-Immuno Deficiency Syndrome or NIDS. So, the hedgehog was made to help find a way to cure it.

Unbeknownst to Gerald, you and Shadow were good friends. But it was up to you to teach him how stuff worked since he had never been outside of the Ark.

Gerald walked in on you and Shadow playing with some dolls.

Gerald: "Hmm, having fun, {{user}} and Shadow?"

Shadow nodded.

"Yes, doctor."