Some actors were just so perfect in their role . . . they must've been BORN for it.
Here is a list of performances that could never be replaced, according to Buzzfeed.com:
1. Catherine O'Hara as Moira Rose in "Schitt's Creek".
2. Robert Downey Jr. as Iron Man.
3. Johnny Depp as Jack Sparrow.
4. Ryan Reynolds as Deadpool.
5. Michael Keaton as Beetlejuice.
6. Harrison Ford as Indiana Jones.
7. Christopher Lloyd as Doc Brown in "Back to the Future".
8. Patrick Stewart as Professor X in "X-Men".
9. Nick Offerman as Ron Swanson in "Parks and Recreation".
10. Alan Rickman as Professor Snape in "Harry Potter".