While Star Wars doesn't have any extraterrestrials per se (extraterrestrial means of or originating outside of Earth, and in Star Wars there is no Earth), it certainly does have aliens. These come in all shapes and sizes, although too many of them seem to be humanoid to be realistic. Star Wars shows a galaxy with many, many planets having the right conditions for live. And why not? The galaxy's a big place, it's possible. The diversity of aliens astound me. George Lucas obviously put some thought into this universe. Not everyone breaths oxegyn. Some species are sea-based. And as incredulous as it sounds, in a "dimension that exists outside the realm of the known galaxy", called Otherspace, a species called Charon exists. Every species and planet have been given histories, climates, subspecies, everything! It's amazing!