Not only was it a puppet, but they even got the original voice-actor/puppeteer Frank Oz to provide the voice and operate the puppet.
And if you were wondering, yes, it is Frank Oz puppeteering the whole
scene, reuniting the cinema veteran with Mark Hamill decades after
they first appeared onscreen together.
“Frank came back, and Frank puppeteered and performed the entire
thing,” Johnson said. “The whole thing is a practical performance by
Frank.
“And seeing him and Mark work together…I’ve got pictures I’ve been
sitting on for the past two years that I can’t wait to put out, of
Frank Oz down there with the Yoda puppet. It was extraordinary.”
...
Neal Scanlan and his team did a recreation of the Yoda puppet. It’s
not only a puppet, it’s an exact replica of the Empire puppet. They
found the original molds for it. They found the woman that painted the
original eyes for Yoda. Then Frank came and worked with them for a few
weeks to get the puppet right. He did a lot of testing and a lot of
adjusting with the puppet creators. It was amazing to watch the
process. The idea that the last time Luke saw Yoda was in Return of
the Jedi and the notion of getting back to that version of Yoda to
form the emotional connection with Luke – including a glimpse of the
impishness, as part of their relationship. It made a lot of sense.”
How Star Wars: The Last Jedi brought back THAT surprise character
and
“He was 100 percent puppet,” writer/director Rian Johnson told Wired. “We actually recreated the puppet from The Empire Strikes Back. They found original molds, and Frank Oz came out and puppeteered him. It was exactly the way they would’ve done it when they shot Empire.”
How Star Wars: The Last Jedi Recreated [SPOILER]
and
ILM sent a giant crate filled with nearly 40 years of material, a time
capsule that doubled as a treasure chest for Scanlan.
"As we opened the boxes, it was cleary evident that each model we took
out was from a more recent model," he recalled. "Then we got to the
very bottom, and there was this wooden box and I could tell instantly
that that was an original Yoda mold that Stuart Freeborn made.
"As we undid it, there was the original head of Yoda," Scanlan added.
"That and one hand were the only two things that we had to go on."
![enter image description here](https://cdn.statically.io/img/i.sstatic.net/VVbNf.png)
Scanlan and his team supplemented those building blocks and schematics
with second-hand research that included conversations with old ILM
employees and puppeteers, as well as studying video they found on the
internet. They also had the luxury of conferring with Oz himself. One
of Scanlan's first big professional jobs was on the Oz-directed big
screen adaptation of The Little Shop of Horrors, and they knew each
other from the Henson Creature Workshop, where Scanlan was a founding
member.
"He was one of my idols and to have worked with him then, he couldn't
walk away from it," Scanlan said, laughing. "There was too much
enthusiasm from our department. I think he would have never been able
to live with himself."
As much as they wanted to recreate Oz's original Yoda puppet, the
creature team didn't shy away from utilizing small advancements to
assist in the performance.
"We wanted to make the technology a little more reliable and a little
bit more user-friendly," he said, "but knowing that Frank was going to
perform it, we just wanted him to feel that he was engaging with this
puppet in a way that was completely and utterly intimate to him.
That's what puppetry is all about: the ability to portray and convey
the emotions of the puppeteer behind it, you know? No greater puppet
than Yoda and Frank Oz."
EXCLUSIVE: HOW A BELOVED STAR WARS PUPPET WAS REBUILT FOR A LAST JEDI CAMEO