‘Project Hail Mary' Writer Shoots Down Theory About Ryan Gosling's Co-Star

The writer behind “Project Hail Mary” shot down a popular theory about the film.

Speaking to Newsweek, author Andy Weir revealed the surprising origins of its alien star Rocky, a multi-limbed, rock-like creature who features alongside Ryan Gosling‘s former biologist-turned-schoolteacher, Ryland Grace.

“He’s water-based, his cells,” Weir explains. “So Rocky is about 300kg of mass, but only about 22kg or 23kg of actual living tissue. So it’s basically like if a beehive had legs and could move.”

In the hard sci-fi film, Rocky’s biology is never explicitly detailed. However, its obvious rock-like appearance suggests it’s a unique example of non-water-based life.

Throughout the film, Grace is ostracized from the scientific community for his controversial theory about life relying on water. Rocky’s seemingly non-water-based existence would have finally proved Grace right.

That’s not the case, however, and for Weir, this marks a key distinction between the film and the novel on which it’s based.

“So in the film, Rocky’s biology is never made clear. In book, it is made clear that all of the life that you see is water-based, and that grace was just wrong.”

Rocky also has another interesting origin: puppetry. The creature is a product of multiple talented puppeteers, with head puppeteer James Ortiz also providing the voice. In fact, almost all the time you see Rocky on screen, it’s a practical effect, not CG.

Ortiz night not be a well-known name to general audiences, but for Weir, he was perfect for the role.

“We were going to get some celebrity, well-known person to voice Rocky, which makes sense, because big-time celebrities are much easier to get for a film if all they have to do is spend a couple of days in a recording booth near their home … But, I think, after a while, we all just went, ‘well, James is Rocky.'”

“We were like, ‘this works, this works really well. Why mess with it?’ Just to get another recognizable name on the movie poster? It’s not worth messing with this thing that is working.”

‘Project Hail Mary’ Release Date

“Project Hail Mary” is scheduled for release in theaters on March 20, 2026.

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This story was originally published March 12, 2026 at 4:10 PM.