 Kaufman said of the casting of Nimoy, "Leonard had got typecast and this [film] was an attempt to break him out of that," referring to the similar quirks that Dr. Kibner and his pod double had in common with Spock, the "Star Trek" character that Nimoy was most well known for.According to Kaufman, it was Mike Medavoy, then head of production at United Artists, who suggested the casting of Donald Sutherland.Sutherland's character had a similar curly hairstyle as that of another character he portrayed in "Don't Look Now" (1973).