Alien costumes can be made in a wide range of styles with the most famous examples probably being little green or grey men costumes and the Klingon or Predator type costumes. More advanced alien costumes include those that look like the large headed half lizard and half humanoid creatures from the Aliens series of movies. There are also many great examples of giant homemade alien costumes that require the wearer to use stilts. The good news is that you can’t really make a “wrong” alien costume because in theory they could come in any shape, size or color. So you can do anything from simply wearing a third eye stuck to your forehead all the way up to dressing up as a giant jelly like creature with 100 eyeballs!