Essentially a bite-sized serial, Superman and the Mole-Men picked up where the Kirk Alyn serials left off and paved the way for the smash-hit TV series that immediately followed: The Adventures of Superman. When ALyn balked at the paycheck, George Reeves assumed the roles of Superman—"valiant defender of truth, justice, and the American Way"—and his alter ego Clark Kent, "mild-mannered reporter for a great metropolitan newspaper."
Assigned to cover "The World's Deepest Oil Well," Daily Planet planet reporters Kent and Lois Lane (Phyllis Coates) arrive in Silsby to discover the well has been mysteriously shut down. The hidden reason: furry, radioactive mole-men on the loose. Yes, Superman and the Mole-Men hinges on the bad-science conceit that the center of the Earth is a hollow home to pint-sized critters with large, bald craniums and bushy eyebrows. It's not enough to believe a man can fly?
I kid because I love. Even at under an hour, this children's fantasy is sluggishly paced by today's standards (you might want to fast-forward through the extended foot-chase with the dog-armed mob hounding the mole-men), but it does have its charms and a relevant social message at its core. Aside from the depiction of a "first contact" gone horribly wrong (the middle-earth "aliens" are terrified), Superman and the Mole-Men uses mob mentality as more than just a useful plot point.
Luke Benson, a rabble-rouser played by veteran Jeff Corey, represents the misguided hysteria at anything or anyone different, and the implicit criticism of the bloodthirsty mob was, in 1951, the kind of social subversion science-fiction could more comfortably couch (director Lee Sholem ruthlessly but effectively rips off Frankenstein for a subplot in which a radioactive mole-man befriends and unintentionally threatens a guileless little girl).
As Lane, Coates is a suitably tough cookie ready to take a swing at her male attackers, and the manly Reeves brings warmth to his iconic characters. The action may not be world-class, but Leonard Maltin's Movie Guide misremembers it: Superman does fly. One shot is animated, and one is live; the famous whooshing sound effect is in place, and Reeve's take-offs and landings were already convincing. The Man of Steel also gets to bend a rifle, and deflect bullets and the mole-men's ray with his chest. Sholem also anticipates later sight gags by giving a hobo a double-take at the fantastic feats of Superman.
[Note: Superman and the Mole-Men was later repurposed as two episodes of The Adventures of Superman: "The Unknown People," Parts I and II.]