(CNN)When director Rian Johnson visited Ireland's Skellig Michael, where Luke Skywalker made his self-imposed exile in "The Last Jedi," the craggy island was so overrun with puffins he had to take care not to step on them.
Instantly he knew the island, called Ahch-To in the film, would also be home to the Star Wars version of puffins, called porgs.
It's the great not-so secret sauce behind the appeal of creatures in Star Wars. The alien species on the screen intrigue but don't overwhelm the human imagination because they're rooted in familiar animals we know on Earth. And the diversity of creatures matches the variety of planets in the Star Wars galaxy -- as much as it does the environments on our own planet.