The phrase "Whoa Nelly!" originated with Pat Brady. Nelly was short for Nellybelle, the name of his cantankerous Jeep. He used the phrase in nearly every show while racing after the villains or rushing for help.
Roy's hunting guide was Carl Switzer. Switzer was a former child actor best known as "Alfalfa" in the "Our Gang"/"Little Rascals" shorts. Rogers threw some extra work his way by casting him in the show as Dale's nephew.
Roy Rogers was unhappy with the penny-pinching producer throughout the production. The actor complained about not being paid enough.
Was a radio show before the tv show, 1944 to 1955.