They Think They're Immortal Morgan Earp, Wyatt's younger brother arrives in Dodge City wanting to be a deputy marshal with Wyatt. Wyatt believes it is too dangerous but pressure from Doc and Morgan proving his strong ability with guns forces Wyatt to reconsider. Details Casts Title They Think They're Immortal Genres Drama Western Release Date 1957-05-28 Episode Runtime 00 Hours 41 Minutes Season Number 2 Episode Number 38 Production Companies sfm Entertainment, Desilu Productions, Wyatt Earp Enterprises Hugh O'Brian Wyatt Earp