ET's Kevin Frazier led a roundtable interview with Interstellar stars.
ET's Kevin Frazier led a roundtable interview with Interstellar stars Matthew McConaughey, Anne Hathaway and Jessica Chastain, getting them to open up about their top-secret experiences on set.
In the three-hour film, out Nov. 7, Matthew and Anne play astronauts who must find a new planet to replace a dying Earth. In addition to the high-stakes premise, the emotional aspect of the tale focuses on Matthew's character who is a father grappling with the conflict of having to leave his children behind for a larger cause: survival of the species.
VIDEO: New Interstellar Trailer
Director Christopher Nolan kept many details about the film under wraps, in true Nolan fashion, storing the script in a locked briefcase with a security guard when not in the hands of the actors.
Keeping secrets for so long may have helped the stars to create an immediate bond. None of the stars had been close before filming, but they soon got to know each other well.
"If you're struggling in a day, just ask yourself, 'How would Matthew McConaughey make this fun?' and that will usually lead you to a better day than you were previously having," said Anne, revealing an important lesson she learned from her Oscar-winning co-star.
Another tip from Matthew -- bring your home with you.
NEWS: Interstellar Stars Flunk Space Quiz
"I should get an Airstream trailer, and take it on every movie I'm doing so I'm not staying in a weird hotel and I can eat my own food," said Jessica, referring to the 34-foot trailer that Matthew brings with him when he's on the road shooting movies.
As a father of three, traveling isn't as easy as it used to be for Matthew, but he revealed to Kevin that his six-year-old son Levi provided part of the motivation needed to tackle the epic project.
"The main impetus in my gut was I want to do this for my son, Levi," said Matthew. "He came to set and he saw all of our shuttles and the Endurance and everything, and he got to take some practical rides, and it was real for him. It was better than Disneyland."
While Anne doesn't have children yet, she does take issue with paparazzi that take unwanted photos of celebrities' children. Watch the video to find out her response to the question: Would you give up your Oscar to eliminate paparazzi?