 In the episode "Trapped In The Sky", Alan Tracys voice is  completely different from all the other episodes that he appears in.  In his single short line of dialog, he is voiced by  Ray Barrett (I) (qv), although Matt Zimmerman (I) (qv) (who did  Alans voice for the rest of the series) is credited in the closing  titles (Zimmerman had not yet been asked to do Alan Tracys voice).