Angelina Jolie and Robert Downey Jr. were original stars of Alfonso Cuaron's 'Gravity' before Sandra Bullock and George Clooney [VIDEO]

Alfonso Cuaron's Gravity was one of the highest rated films of 2013 and has been getting lots of recognition and awards ever since its release. But the film could have been a completely different film if it wasn't for Cuaron's decision to recast the leading roles early on in the production. According to a new interview with Cuaron, George Clooney's role was originally filled by Iron Man star Robert Downey Jr. and Sandra Bullock's role was originally Angelina Jolie's.

"I thought I had written a small movie ... just one character floating in space," Cuaron told The Hollywood Reporter. "We started developing stuff [trying] to figure out the technology. And the luxury [was] that we could try many things. And part of that was conversations with actors. I had conversations with Angelina, but then she went to do one film, and then she was going to direct [Unbroken]. Something happens, you part ways."

Jolie's busy schedule led to Bullock's casting, which led to her Oscar nomination for her role!

"It became very clear that, as we started to nail the technology, or narrow the technology, that was going to be a big obstacle for his performance," Cuaron said about his original casting choice for George Clooney's role. "I think Robert is fantastic if you give him the freedom to completely breathe and improvise and change stuff. [But] we tried one of these technologies and it was not compatible. And, after that, we [had a] week that we pretended as if nothing was happening and then we talked and said, 'This is not going to work. This is tough.'"

Watch this interview right here: