Matt Damon's Interstellar Cameo, Explained

"Interstellar" represents a lot of firsts for Christopher Nolan. The 2014 sci-fi movie was the first time the director infused one of his stories with some real heart and treated it as if it were just as important as any of the philosophical musings which typically guide his films. As such, "Interstellar" became Nolan's heartfelt masterpiece, not only making time for emotional exploration but also arguing for love itself as our only means of transcending the inexorable march of time.

"Interstellar" was also the first time Nolan worked with DP Hoyte van Hoytema, who has since served as cinematographer on three of the British director's other films (including the movie that dominated the 2024 Oscars, "Oppenheimer"). It was also the first time Nolan worked with Matt Damon, who for a long time had been an outspoken fan of the director. Even after his brief appearance in "Interstellar," Damon was angling for a bigger role in a Nolan film, which he eventually got by playing Lieutenant General Leslie Groves, the man who oversaw the Manhattan project, in "Oppenheimer." Indeed, in that case, Nolan was the only director who could end Damon's acting break.

In "Interstellar," however, Damon's role was a much smaller one — though it was hardly insignificant. Here's everything you need to know about Matt Damon's "Interstellar" cameo.

In "Interstellar," humankind finds itself on the brink of extinction after a planet-wide blight threatens the future of crop growth. The solution? Matthew McConaughey. Or, more specifically, McConaughey's Joseph Cooper, a widowed ex-NASA test pilot who's sent into space to travel through a wormhole near Saturn. On the other side are a dozen planets that may or may not be habitable by humans. Cooper is tasked with investigating the planets and identifying a suitable world on which to build a colony, either by shipping the human race from planet Earth (plan A) or by delivering 5000 cryogenically frozen embryos to the planet (plan B).

On Earth, NASA scientist Professor John Brand (Michael Caine) continues developing a series of ships to transport the global population to this new planet. But he needs quantum data from Cooper's trip in order to create a gravitational propulsion theory that will allow the ships to function. Should Cooper fail to find the data, then the pilot and his crew must turn to plan B (more on that later).

Once Cooper and his crew make it through the wormhole, they land on a planet previously visited by a Dr. Mann, played by Matt Damon (who, interestingly enough, had previously turned down playing Two Face in Christopher Nolan's "The Dark Knight"). Mann was the leader of what was known as the Lazarus expedition, a previous mission that saw him and fellow scientists Miller and Edmunds travel through the wormhole to evaluate the mysterious planets on the other side. Mann had since sent back a signal to confirm that the world on which he landed could support human life. When Cooper and the crew discover him, Mann has been in a state of cryostasis for some time, and Cooper has to break the pod to revive him.

When Joseph Cooper and his crew first travel to Mann's planet, they are optimistic. After all, the doctor previously transmitted data that suggested the ice world was able to support human beings. As such, when Dr. Mann is revived from his cryostasis, there's hope that he and his planet might just be able to help save the human species. However, soon after arriving on the world, Cooper discovers that Professor John Brand, back on Earth, lied to him prior to the mission launch. The scientist knew that transporting humans from Earth to a new planet wouldn't work as his gravity theory was incomplete and could only be finished with data taken from inside a black hole. As such, he intended for Cooper and his team to go through with plan B and colonize another planet rather than returning to Earth with the data needed to transport the entire human race to a new planet.

Things continue to go downhill after this revelation, with Mann admitting that he also knew Brand's Plan A wasn't feasible. Hen then proceeds to try to kill Cooper and admits that he falsified the data showing his planet was hospitable to humanity. He did so in order to bring a crew to his location so that he could be rescued from what is essentially a giant ball of ice. Cooper is saved, but one of his crew members is then killed by a booby trap set by Mann, who then steals the crew's landing aircraft. He subsequently attempts to dock it on the larger Endurance spacecraft, only to be killed after the airlock depressurizes during docking. 

This severely damages the Endurance itself, forcing Cooper to change his plans and venture directly into the heart of the giant black hole Gargantua (which turned out to be a highly accurate rendering of an actual black hole). As such, Matt Damon's character is arguably the main villain of "Interstellar," as his selfish ambitions almost jeopardize the entire Endurance mission and result in the death of a crew member. While Professor Brand himself lied to the whole crew in order to get them to carry out his Plan B (colonizing another planet), Mann is more immediately treacherous and selfish.

Anyone going to see "Interstellar" in 2014 was likely surprised to see Matt Damon in the role of Dr. Mann. Here was a big star playing a part small enough that it was essentially an extended cameo. But it seems Christopher Nolan wanted it that way, as he made sure Damon (who will soon portray Odysseus in Nolan's upcoming adaptation of "The Odyssey") wasn't in any of the promotional materials for the movie, thereby keeping his appearance a secret from audiences.

Even without that surprise element, the fact that Damon played such a small but important role made the whole thing that much better. In a film where time's unstoppable march is arguably the main villain, Damon's presence gave the film a recognizable antagonist. Using an established star for the role of Mann also emphasized the importance of the part. Though Mann only appears in "Interstellar" for a short time, his actions change the course of the whole Endurance mission. This ultimately sends Joseph Cooper into the heart of a black hole, which is where he discovers the quantum information needed to transport the entire human race from Earth to a new planet at the end of "Interstellar."

As such, Mann plays an important role, even if Nolan didn't necessarily see it as such. Speaking to Fandango, Damon recalled being offered the part, saying "Chris is very direct. Like when he offered me 'Interstellar' years ago, he said 'You know they say there are no small parts, there are only small actors?' and I'm on the phone and go 'Yeah!' [And he replies] 'This is a small part.'" Still, the director clearly knew that Damon's presence was going to be a big hit with audiences, which is why he kept the actor out of all the marketing materials for the film.

Alongside the launch of "Interstellar" in November 2014, Christopher Nolan wrote a seven-page comic published via Wired (and readable in full here), which served as a prequel to the film. Illustrated by Sean Gordon Murphy (with colors by Matt Hollingsworth) and titled "Absolute Zero," the comic is set prior to the Endurance mission and finds Dr. Mann, having departed on the Lazarus mission, stationed on his planet alongside his robot KIPP (so named for theoretical physicist Kipp Thorne, who served as an advisor to the movie and is a huge part of the reason "Interstellar" is so scientifically accurate).

The story follows Mann and KIPP as they retrieve their probe, which had drilled into the core of the planet and returned to the surface with data explaining the makeup of the world. After KIPP scans the data and finds no evidence of any solid ground under the sheets of ice, Mann knows for sure that his planet is inhospitable for humans. Interestingly enough, even prior to retrieving the probe, we see that Mann has asked KIPP to produce "hypothetical" data sets showing his planet to be the ideal place for a human colony, suggesting he knew for some time that his world was a dud.

After Mann and KIPP clash, they return to their base. There, Mann asks for the hypothetical dataset before accessing KIPP's parameters and taking him offline to ensure the robot doesn't see him transmitting the fake data to Earth. With KIPP offline, Mann sends the data, thereby setting in motion the events that bring Cooper and his crew to Mann's planet in the film.