Earth is the third planet of the Solar System, located in the Milky Way Galaxy, and the homeworld of the Human race. Unlike Melmac, Earth is round shaped and has green grass, blue skies and a single moon. Earth also is composed of several techtonic plates which causes hundreds of earthquakes per hour, while Melmac has no tectonic plates and presumably entirely made of one layer. Approximately one year after the destruction of Melmac, ALF crash lands his spaceship on Earth, specifically in the Tanner family's garage. He remains at the Tanners for about four years before he is captured by the Alien Task Force. He escapes the Alien Task Force and is eventually granted the position of intergalactic ambassador to Earth. Melmacians seem to have a broad knowledge of Earth cultures, perhaps through years of observation. For instance, ALF is known to have once participated in a dinner theatre production of Man of La Mancha on Melmac, a musical that was written and composed by humans. Earth and Melmac probably seem to share biology similarities as cats exist on both planets, and ragweed is similar in appearance and medicinal effect as Melmac's Carl Shrub. Additionally, ALF's The Furry Home Companion lists raw spinach as a cure for hiccups. Gold is extremely valuable on Earth, even causing frenzied gold rushes and being used as a fiscal standard, but on Melmac, gold was so plentiful it was valueless and was often used for plumbing fixtures.
Earth has never encountered any alien species besides ALF. Since many humans have developed a fear of strangers, searching for extraterrestrial life has become common, even aligned with the government.