Yeah, it’s crazy. Popeye’s voice is actually two voices an octave apart, which creates some really neat partials (overtones). No idea if the original guy knew it was Tuvan throat singing-ish things he was doing, but Billy West figured it out. And if it weren’t for Billy West, we wouldn’t have Futurama or the original Ren and Stimpy (and we all know how well it fared when it came back without him).
Billy West explaining Popeye’s real voice via Tuvan Throat singing methods