Sergeant Preston of the Yukon was a television series which followed from the radio drama Challenge of the Yukon. Richard Simmons starred as Sgt. Preston, and was supported by his dog Yukon King and horse Rex, now played by real animals. The dog cast as King was not a husky, however, but a large Alaskan Malamute. Charles Livingstone, who had worked on the radio version, directed several episodes. Though no plotlines seem to have been re-used from the radio show, they were generally built upon the same themes.