Transplanting Animal Fur to Human Heads?

You mentioned joking about transplanting animal fur to human heads.

Why isn’t this possible? Only because of an immune response to the hairs as a foreign body?

What animal did you have in mind? As if fur coats aren’t bad enough, what would PETA say?

You answered your own question — the body’s response to the hairs would prevent transplanting animals to humans (or humans to other humans, unless they are identical twins).