What If 'Looper' Stars Could Time Travel?

Joseph Gordon-Levitt is a time-traveling hit man tasked with taking out the older version of himself -- played by Bruce Willis -- in the futuristic thriller Looper, in theaters September 28, and the film's star trio talks about their passion for the project – and what they would do if they could time travel.

Video: Time-Travel Trio Premieres 'Looper' in Toronto

"Well I'd quite like to go to the '20s or something. I think that could be really fun," Emily Blunt tells ET's Christina McLarty, adding, "But there's also a part of me that is really intrigued to go back to, like, the birth of time and see the cavemen, what that must be like, what people actually looked like. I want to see those dinosaurs. Like that would be so exciting to see when people first starting drawing and discovering art and food and medicine and all that stuff."

In Looper, time travel is illegal and only available on the black market. When the mob wants to get rid of someone, they send their target 30 years into the past, where a "looper" -- a hired gun, like Joe (Gordon-Levitt) -- is waiting to mop up. Joe lives the good life with his job as a looper – until one day the mob decides to "close the loop," sending back Joe's future self (Willis) for assassination. Will he kill himself, or team up to get revenge?

"It's a movie about how violence begets violence and how that's a cycle, and it asks the question can you solve the problems of violence with more violence, or is that just an endless loop," explains Gordon-Levitt. As for having Bruce Willis play his future self, he smiles, "That was a fist-pump moment for me when we found out that he dug the script and he wanted to do it."

Video: Joe & Emily are Loopy for 'Looper'

And Willis gives his stamp approval on the project, saying, "I'm quite passionate about this film. I'm struggling with the idea that this could be one of the best film's I've ever worked on -- or the best film I've ever worked on. I've been in some cool films."