I got a question for you: Jonathan Harris (born Jonathan Daniel Charasuchin; November 6, 1914 -- November 3, 2002) was an American character actor. Two of his best-known roles were as the timid accountant Bradford Webster in the television version of The Third Man and the fussy villain Dr. Zachary Smith of the 1960s science fiction series Lost in Space. Near the end of his career, he provided voices for the animated features A Bug's Life and Toy Story 2.

Answer this question: who played dr. smith in the original lost in space series?
Let's think first:
This is the relevant information: Two of his best-known roles were as the timid accountant Bradford Webster in the television version of The Third Man and the fussy villain Dr. Zachary Smith of the 1960s science fiction series Lost in Space.
Therefore, the answer is Jonathan Harris.