John Gabriel played the "Professor" in the unaired pilot of Gilligan's Island (1964).
This pilot also has a different theme song, composed by John Williams.
[on losing the role of the Professor after he played the character in the Gilligan's Island pilot] It was the first time in my adult life that I remember weeping. And I think part of that has to do with the fact that I built this thing up to such a degree it was going to be my breakthrough.