For non-stop laughs, it's "The Phantom Empire", a B Western that combines the genre with Sci-Fi! Gene Autry rides into a cave after some bad guy, and follows him down in a supersonic elevator to an underground world of aliens. You can tell the aliens, because they look like people dressed up in tin foil suits wearing buckets on their heads. An all-time classic, and I love it. Oh, and by the way, Gene sings a few tunes, and plays the D-45, too!!