https://www.metv.com/stories/jim-nabors-wanted-audiences-to-know-that-gomer-pyle-wasnt-stupid

"He only saw good in other people, which most people think is stupid," said the actor.

Frank Sutton used his real military experience on Gomer Pyle: USMC (https://www.metv.com/stories/frank-sutton-used-his-real-military-experience-on-gomer-pyle-usmc)

Sutton was a real Army veteran with a fictional Marine background.