Quite possibly, the most talked about thing going into Star Wars: The Last Jedi wasn't Luke Skywalker or Rey, it was the porgs. The cute little seabirds got a ridiculous amount of attention, and after seeing the film, we can't get the sound they make out of our head. It turns out the call of the porg is the result of combining the sounds of a number of different birds together. According to sound designer Ren Klyce, the process started by recording the sounds of a chicken coop on the grounds of Skywalker Sound, before moving on to record doves and turkeys. As Klyce describes...
At Skywalker Sound there's a chicken coop with these little chickens, and Coya Elliott, our first assistant, went down and recorded those chickens. And then we took that sound and slowed it down and stretched it out and found little chirps. We found this man who releases doves at weddings, and we asked him to come down so we could record them...So we have a little snippet of that [turkey call], a little bit of chicken, a little dove, and cut it all together.
The combination of sounds came together to create a call that seemed to fit the progs perfectly. It certainly had bird elements to it, but it was also somewhat alien, which is likely exactly what the sound crew was going for. The porgs ended up with a significant amount of screen time, surprising considering that they never really played a part in the actual plot. But they're just always around. The sign that the Skywalker Sound team did their job right was that the sound of the porg never gets annoying, which, according to D23, was one of the edicts laid down by Star Wars: The Last Jedi director Rian Johnson.
Overall the porgs were an interesting diversion that added some lighter moments to The Last Jedi. Chewbacca's attempt to eat one, while other porgs look on, is probably a moment that's going to stick with a lot of people. While it was a humorous scene, it's a dark humor that we rarely see in Star Wars. It's never clear whether the Wookie actually eats the little creature or eventually gives up.
The other remarkable thing about the creatures is that, while they make appearances throughout the film, they're never directly addressed, in fact, the name porg, like Ewok before it, is never uttered throughout the film, showing how powerful the Star Wars marketing truly was in the lead up to the movie. We all know what a porg is, even though the characters in the movie may not actually realize that's what they're called.