^ And Tony Randall as Mr. Spock. Walter Matthau as Dr. McCoy.
Actually, Klugman is a pretty good choice. He had plenty of gravitas for a role like Captain Kirk (or Winter or Pike or whatever).
As to my additions, well, Matthau could certainly do gruff at McCoy-plus-ten levels. But I have a hard time imagining Tony Randall as an emotionless alien.