 The face of the Alan Tracy puppet was modelled on actor Robert Reed.Matt Zimmerman voiced the character for all but one of his 1960s appearances; since Zimmerman was a late addition to the cast, Ray Barrett provided Alan's voice for his debut appearance in the series opener, "Trapped in the Sky".Zimmerman was recommended to producers Gerry and Sylvia Anderson by David Holliday, the voice of Virgil Tracy.