Aliens are defined as any living thing not originating on our earth. Speculative forms of extraterrestrial life range from humanoids and monsters beings seen in works of science fiction to life at the much smaller scale of bacteria and viruses. A good alien abduction story brings nut cases out of the woodwork. Famous Roswell Case: alien autopsy Extraterrestrial life forms, especially intelligent ones, are often referred to in popular culture as aliens or ETs. It's said that aliens usually come to Earth with UFOs. Strange lights in the sky, large metal objects with unknown powers, and strange abilities all contribute to fear and dread.  A UFO or Unidentified Flying Object is simply defined as any object or optical phenomenon observed in the sky which cannot be identified, even after being thoroughly investigated by qualified people. The existence of extraterrestrial life remains hypothetical though human beings continue their searching. The Roswell alien has become an ongoing curiosity in the town of Roswell, New Mexico, USA.  There is an annual festival and an alien museum where you can buy assorted replicas and other items.