Best Actor?

John Cazale is not a household name, but he should be. When the actor died at age 42, he'd made only five films, but every one was nominated for best picture:

The Godfather
The Conversation
The Godfather: Part II
Dog Day Afternoon
The Deer Hunter

That alone would have made him unique in Hollywood history, but he added a hat trick. In 1990, 12 years after his death, Francis Ford Coppola used archive footage to include Cazale in The Godfather Part III (as Fredo Corleone).

That too was nominated for best picture.