Baby Yoda, the breakout Disney Plus creature of the moment, would never have snuggled into the zeitgeist if the rotors and motors and animatronic tics of his wizened green forebear hadn’t clicked into place exactly 40 years ago.

In 1979, Yoda was more than another rubber puppet coming into gradual being on the set of “The Empire Strikes Back.” The Jedi Master’s small mechanized frame embodied the hope and fate of the entire enterprise. The character was a “real leap,” Star Wars creator George Lucas said in a 2004 documentary, because “if that puppet had not worked, the whole film would have been down the tubes.”

Casting the right actors is one thing, but in a space opera like Star Wars, getting a creature to resonate on-screen can be a far more complex undertaking, requiring the brilliance of so many veteran hands. And after more than a dozen feature films and TV projects, there is still no surefire formula for building the ideal Star Wars critter. Just ask (ahem) the minds behind Jar Jar Binks.

As “The Rise of Skywalker” opens Friday, bringing the epic family saga to a seeming conclusion, the J.J. Abrams-directed movie will remind viewers that since 1977, no mass franchise has given us more iconic new film creatures than Star Wars — a steady march of unique and irresistible creations.

How does Star Wars do it? Even if “I knew that special-sauce recipe,” said Chris Terrio, the Oscar-winning co-writer of “Rise of Skywalker,” “I certainly wouldn’t publish it.

“Whatever they’re doing with Baby Yoda,” he continued, referencing the character actually named the Child from the new streaming series “The Mandalorian,” “I want to know more.”

“Rise of Skywalker” introduces a wealth of new creatures — including the tiny repair puppet Babu Frik and the vulnerable small droid D-O — which presented a heady challenge. “You’re not just standing on the shoulders of those who have designed before,” Abrams says by phone from the Los Angeles area. “You’re also surrounded by, and in the shadow of, all the designs that preexist you.”

To rise to that high creative bar, Abrams bore in mind that some of the qualities that make for an engaging creature are identical to the traits of an interesting human character within Star Wars — which, he says, is centered on “behavior and, depending on the role intended, a level of sympathy, which usually has to do with the eyes.”

“The trick is just to mock it up and keep going,” he says, “and in my case, working with amazing designers and artists who are part of that conversation.”

For some of the franchise’s beloved creatures, naturally, the talent of the actor beneath the hardware and plastic is crucial — especially with characters that become true scene-stealers.

Muppets creator Jim Henson, brought aboard to work on Yoda, chose his right-hand man Frank Oz (Miss Piggy, Fozzie Bear) to become the character, for instance, because Oz was “admired for his ability to create characters nearly at will,” writes Brian Jay Jones in his biography “George Lucas: A Life.” Oz, as much dramatic actor as physical puppeteer, spent long months before the “Empire” shoot working out how to bring Yoda to mesmerizing life.

Oz and Yoda became so seamless that “Empire” director Irvin Kershner often “found himself giving direction straight to Yoda rather than addressing his comments to Oz,” writes Jones, adding: “Even Lucas could get caught up in the moment, sitting cross-legged in Yoda’s home, completely wrapped up in conversation with the puppet, even with Oz in plain sight.”

Yoda represents the franchise’s pinnacle of geniuses coming together, Jones said by phone from New Mexico.

“In the creation of Yoda, Lucas and Henson were each relying on the creative expertise of the other,” Jones said of the teaming of Henson’s Creature Shop and Lucas’s Industrial Light & Magic. “Lucas needed Henson’s group of talented puppeteers and performers who could figure out how to build, create and perform a believable character — and Henson wanted to get his hands on the technology that Lucas and ILM had developed for building that character.

“It was a kind of ‘tech transfer’ between the two men and their two companies, in pursuit of something bigger than just one of them — and that something that was Yoda.”

Beyond Oz, another actor who especially defined his creature is Anthony Daniels, who has voiced C-3PO across 42 years, including in “Rise of Skywalker.” Lucas initially envisioned the service droid as a slick car salesman type, Jones said, but it was the Wiltshire-born Daniels who hit upon the “fussy English butler” sound for Threepio.

Many of the most memorable Star Wars creatures share a human element, even when viewers might not realize it. In the case of the droid R2-D2, for example, Lucas and Oscar-winning sound designer Ben Burtt wanted an “organic sound” within all the whirring, according to Jones, so they recorded themselves “cooing, whistling and beeping and ran it through a synthesizer.”

Kirk Thatcher, a Muppet director and writer who was a creature technician on “Return of the Jedi,” offers a related theory: Since Star Wars is so story-driven, the filmmakers don’t present creatures simply to flash their artistry.

“Characters in this universe have a point of view,” Thatcher said, “even if it’s just a menacing alien.” And that point of view is conveyed through whatever registers as a “face,” he said, as well as the visual “attitude” of the head and even the character’s size. Thatcher noted that Star Wars made sure to vary the sizes, and that too many earlier sci-fi creatures were of similar scale to humans. (On the original “Star Trek” series, Thatcher said with a laugh, so many of the aliens were curiously close to 6 feet tall.)

Star Wars designers know how to lean into those size differences for powerful effect, whether the creature is as massive as the snow-walking AT-ATs or the slobbering Jabba the Hutt — or as diminutive as the cowled Jawas on the sands of Tatooine.

When you go small in Star Wars, though, you risk provoking fans who accuse the franchise of pandering toward the adorable — whether it’s through Lucas’s cherished teddy-bear Ewoks of Endor introduced in the original trilogy, the Keane-eyed porgs of “The Last Jedi” or even the wee rolling droid BB-8 that Disney chief Robert Iger had a hand in adding to the galaxy.

“You go too cute, and you disengage some people,” Neal Scanlan, a Muppet alumnus who now works on the Star Wars films, told USA Today in 2017. “Don’t go cute enough, you’re going to exclude younger viewers.”

When you weigh all those factors — the size, the human element, the character design and point of view, the unique communication sounds — perhaps no Star Wars film creature is greater than one: Chewbacca.

“To me, that is the perfect design,” Thatcher said. “I just kind of marvel at the simplicity — he’s not a dog, he’s not a werewolf, he’s not a gorilla. There are so many animals we can attribute his physiognomy to — it’s actually really difficult [to create] — but it’s the perfect amalgam of creatures that we like.”

And beyond the movies, Thatcher concedes the full-circle appeal of Baby Yoda.

“He’s green and cute and humans are so programmed to love that baby kind of layout with those cheeks on a big face,” Thatcher said. “We just can’t stop going, ‘Goo-goo-gaga.’“

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