Rian Johnson may have written the word “Porgs” in the description paragraphs of his script for Star Wars: The Last Jedi, but the reason we know what they are is because of stuffed animals, action figures, purses, backpacks, watches, keychains, stickers, phone cases, and more.
As many in the comments will surely note, a huge part of this phenomenon is Star Wars’ place in the merchandising and marketing.
Thanks to the deal that George Lucas first signed when selling the film back in the 1970s, toys have been a massive part of the franchise from the very beginning, and has helped drill even the smallest details of the universe into the minds of fans.