I recall the Superman episode , “The Unknown People”, which dealt with people who lived underground, but were unknown to us. They were technologically advanced as I recall........
Perhaps they are the source of the huummm.......
Sarcasm.......
Are you talking about George Reeves?
***That Superman episode , “The Unknown People”*** was actually the pilot for the original Superman series. That’s why it was movie length and they had a different actress for Lois Lane.