"It was a beautiful experience, because we all were so passionate about it," Lawrence, 26, said.
"This is the kind of movie that is going to blow you away," said Pratt, 37.
The action-thriller follows two spaceship passengers, Jim (Pratt) and Aurora (Lawrence), who are on a 120-year journey to another planet when their hibernation pods wake them up 90 years too early.
"It becomes very clear that there's something really wrong with the ship, and gravity starts to go out, and the robots are all failing," Lawrence explained. "Jim and I are in a race against the clock to figure out what is wrong with the ship, and how we can fix it -- not just to save our lives, but the lives of the 5,000 people who are on the ship."
"It's all 'What would you do?'" she added. "It's a conversation starter."
Bringing the Avalon spaceship to life became like creating a whole other character in the movie. At one-mile long and five-stories high, the massive structure was designed to resemble a luxury cruise liner.
Huge sets for the grand concourse, the observatory deck and more occupied eight sound stages in Atlanta -- one of them measuring out to 40,000 sq. ft., which is as big as a Walmart.
"When I see the sets that the people on this crew have built, you can't help but be in awe," Pratt said.
In the film, Jim and Aurora have decades of time on their hands as they can only interact with each other, which inevitably leads to them falling in love. Behind the scenes, Lawrence admired Pratt's work ethic.
"Chris Pratt is the hardest-working person I've ever met in my life," Lawrence gushed.
Passengers, also starring Michael Sheen, Laurence Fishburne and Andy Garcia, hits theaters Dec. 21.