Besides the title character, other characters are Orbi (Cosmo's astronaut companion), Professor Thimk (the scientist who invented the Martian spaceship, but was not on it when it took off from Mars), and Astra (Cosmo's girlfriend). In the first issue, while they are traveling toward their intended destination of Earth, a meteor damages their spaceship, and they crash land on Earth's moon. The moon turns out to be inhabited by beings named Oogs, who live underground.