A pigs ear

Recently a man lost his ear, and it was replaced by doctors with a pig's ear.

They trimmed it down a bit and made it look human before attaching it.

A few weeks later and the man goes back to the Doctor and says: "Doctor, I keep hearing this noise and its doing my head in."

To which the doctor replies:

Spoiler:

"Don't worry, its just a bit of crackling"