By now you have most likely seen Star Wars: The Last Jedi. If you haven’t then be warned before continuing, because this article does contain spoilers.

Thala-Siren from Star Wars: The Last Jedi
Thala-Siren from Star Wars: The Last Jedi

One of the classic scenes in the film involved Luke milking some sort of animal on Ahch-To, which he then decided to drink in front of Rey. While it was a gross scene, Mark Hamill pulled off one of the funniest scenes in the film with his reaction to the green milk.

The animal responsible for giving the green milk is known in Star Wars lore as a thala-siren. Think of them as “sea cows”. The species is indigenous to the planet Ahch-To, and routinely hit the shores of the islands for a little sun-bathing. The creatures have udders similar to cows, which when milked, provide a green milk substance.

How the filmmakers decided to give the thala-siren life is an interesting question, and one best left for Lucasfilm’s special effects wizard Neal Scanlan. He talked with the website Nerdist, to give us a better understanding of how the effect was achieved.

They created the entire puppet at Pinewood from foam latex. The thala-siren has a mechanism on the inside so her head could tilt forward “like a submarine hatch.” Scanlan said that allowed two puppeteers to get inside the creature—one in the front and one above him. “One would operate the shoulders and the flippers at the top and the other person would operate the belly and the milking mechanism or the udder mechanism at the bottom,” he said.

About Star Wars: The Last Jedi:

Star Wars: The Last Jedi is currently at theaters nationwide. Directed by Rian Johnson and starring Mark Hamill, Carrie Fisher, John Boyega, Daisy Ridley, Oscar Isaac, Benicio del Toro, Laura Dern, Jimmy Vee, and more! Music will be composed by John Williams.