These are monster movies about monsters, monsters being such creatures as extraterrestrial aliens, giant animals, Kaiju (the Japanese counterpart of giant animals, but they can also be machines and plants), mutants, supernatural creatures, or creatures from folklore such as Bigfoot or Nessie, which is known to experts as perfectly natural. etc. These movies usually are in the science fiction, fantasy or horror genre or more than one of the above, but sometimes can be in a different one. For example, both Monsters Inc. and Monsters vs. Aliens are in the family genre.