Actors/Actresses that cannot be replaced if their films were to be remade.

[Blu-ray Fanatic]

There are many great movies out there that are too classical and there's no possible way the original actors/actresses can be replaced.

For myself, the entire Rocky/Terminator franchise cannot be remade whatsoever because there will be no one to replace Stallone/Aaanold.

Its your turn. Which films, in your opinion, cannot be replaced by different actors/actresses.