Uranus' inhabitants are actually small mechanical robots. Their civilization is quite advanced, they can tour the solar system in circular space ships and although having weapons like "lance throwers" and "flame cannons", they have other advanced technologies like "transporta-rays" (which transport things and animals) and an interplanetary zoo.
In September 1949, referring to a book called "Children's Picture Book of Animals", they try catching an earth animal from each page, including a human man and woman. Superman deceives them into thinking all humans are robots, which they have no interest in (WF No. 6, Sep 1949: "The Alphabetical Animal Adventure").