Julie Andrews as Maria in “The Sound of Music.”
Kathy Bates in Misery.
Most of her roles are spot on though.
James Gandolfini as Tony Soprano.
And yes, I realize his son may end up playing a younger version of that character. But the middle aged Tony could never be portrayed by anyone else.
Christopher Lloyd as Dr. Emmett Brown
Robert Shaw as Quint in Jaws. I don’t think anyone else could have pulled off that level of unhinged sadness without looking completely over-the-top.