Ryan Gosling improvised one of 'Project Hail Mary's best moments

Put Ryan Gosling and an alien puppet in a spaceship, and you get sheer joy.

That's the best way to sum up Project Hail Mary, a good chunk of whose runtime is a two-hander between biologist Ryland Grace (Gosling) and an alien named Rocky (voiced by James Ortiz). In addition to voicing Rocky, Ortiz also served as the creature's lead puppeteer, helming the crew that brought the endearing Eridian to life.

The final version of Rocky audiences see on screen is a marriage of practical puppeteering and animated effects, but Project Hail Mary directors Phil Lord and Chris Miller knew they needed that practical base in order to truly sell Grace and Rocky's friendship.

"It's so important for that core relationship in the movie for Ryan to have a scene partner and someone with whom to bounce things off of," Lord told Mashable in a joint video interview with Miller. "That meant getting a real puppet that we could really photograph, and a great team of puppeteers, led by James Ortiz, that could respond to his improvisational ideas and offer ideas to Ryan so that he would not know what was going to happen next."

Gosling's improvisation and Ortiz and his team's responses lead to one of the film's most charming sequences: when Grace first meets Rocky in the tunnel Rocky has built from his ship to the Hail Mary.

While Grace is terrified by Rocky at first, he soon realizes that the alien means him no harm. They establish trust by mimicking one another's peaceful movements, including some perfectly awkward dance moves by Grace.

Gosling shot the scene with an earwig in, through which Lord and Miller pitched him ideas of gestures to carry out. He was also free to try some of his own.

"We left it to the puppet team to try and copy whatever it was that Ryan was doing, and we would be like, 'OK, do a little dance, or do the Macarena, or draw out a gun,'" Miller recalled. "Every time he would do that, the puppeteers had to figure out how they were going to copy what he did."

Even on set, the effect was one of delight.

"As we were shooting it, it was movie magic. You're like, 'I can't believe we're capturing this thing, and it's really happening.' You can see the joy on Ryan's face as he watches the little alien puppet trying to do whatever it is he's doing, and I think there's something so magical and special about that," Miller said.

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Another improvisational moment for Gosling, Ortiz, and the Rocky team? The scene when Grace gives Rocky a measuring tape in the hopes of comparing numerical systems. Rocky isn't able to read the numbers, and instead plays with the measuring tape much in the way an excitable kitten would play with a ball of yarn.

"We put a real measuring tape in Rocky's hands, and we just told [the puppeteers] to play the game of 'Don't look at the numbers, just mess around. Whatever you do, do not do what Ryan's asking you to do,'" Lord said.

"He was really reacting, going, 'Oh my God,'" Miller added.

So when you're watching Project Hail Mary, remember that even though Gosling is acting, some of Grace's wonder towards Rocky (and perhaps even the occasional exasperation) is totally real.

Project Hail Mary is now in theaters.