The show Supernatural deals with this briefly.
SPOILERS I GUESS
There is someone who discovers a way to become immortal, but his body is constantly degrading so he has to steal working body parts from living people to keep himself functional. So you can cut him up and stuff, but he'll still be alive and you can put him back together if you fix him, aka he will go blind from his eyes getting old, but then he can surgically remove eyes from a living person and put them in himself and that's how he continues "functioning". He will always be alive though.
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