There are many reasons why the Star Wars franchise is special, but a big part of it is its incredibly deep cultural pervasion. While science-fiction as generally seen as niche fare, it's legitimately rare that you find someone who has never seen at least one of the movies. Generations now grow up knowing the legends of Luke Skywalker, Princess Leia, and Han Solo, not only watching their adventures, but engaging with them through endless merchandise. It's a brand so big that everyone in the world knows details about it that aren't even mentioned in the blockbusters.
When the first full trailer for Rian Johnson's blockbuster first dropped, fans immediately became curious about the big eyed, bird-like creature, and that curiosity inspired a pop culture wave. Months before Star Wars: The Last Jedi hit theaters, social media was exploding with Porg chatter and Porg memes, and, of course, stores were flooded with Porg merchandise. Anyone who purchases a ticket to the film this weekend is probably already aware of the creatures, and some are probably even specifically anticipating their involvement.
Despite the lack of namedrop, every Star Wars fan of the future will know exactly what they are -- and I say that with absolute confidence. Why? Because they've done this before. You may have never noticed it before, but there is no scene in Star Wars: Return of the Jedi where the Ewoks are actually called "Ewoks." (None of the human characters know what they are, so how could they?) And yet there are very few people in the world with a respectable pop culture knowledge who don't know what an Ewok is.
It doesn't stop there, either. Emperor Palpatine was first introduced as a presence in the Star Wars universe in 1980's The Empire Strikes Back, and played a significant role in 1983's Return of the Jedi. However, nobody in either of those movies ever says the name "Palpatine." It's featured in the opening scroll of the latter film, but never spoken aloud. And yet many regular movie-goers won't bat an eye before identifying Darth Vader's boss.
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. 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.
Time and further exposure certainly helped "Ewok" and "Palpatine" become Star Wars staples -- lest we forget the two notorious Ewok movies and the latter's increased role -- and we can probably expect the same for the Porgs. They certainly aren't going anywhere any time soon, and before too long everyone will know the name, but never know exactly why.