Academy Award best picture hopeful "Gravity" almost looked a whole lot different, according to director Alfonso Cuarón.

In a 90-minute interview with "The Hollywood Masters," Cuarón revealed that both Angelina Jolie and Robert Downey Jr. were in talks to play lead characters Ryan Stone and Matt Kowalski.

angelina jolie

In the end, Sandra Bullock and George Clooney were cast in the roles, with Bullock's portrayal of astronaut Stone earning her an Oscar nomination. But Jolie and Downey were serious contenders, shared the director.

"I had conversations with Angelina, but then she went to do one film, and then she was going to direct [the upcoming 2014 drama 'Unbroken']," Cuarón explained. "Something happens, you part ways."

Downey got as far as filming test shoots, but it just wasn't working with the actor, said Cuarón.

"I think Robert is fantastic if you give him the freedom to completely breathe and improvise and change stuff," the 52-year-old said of the "Iron Man" star.

"(But) we tried one of these technologies, and it was not compatible. And, after that…we talked and said, 'This is not going to work. This is tough.'"

Downey was then replaced with Clooney as Bullock came on board, and since its October 4th release, "Gravity" has earned more than $700 million at the box office worldwide and scored 10 Oscar nominations, including a best director nod for Cuarón.

sandra bullock

Bullock, Cuarón & Clooney

"I thought I had written a small movie … just one character floating in space," Cuarón said of his 14th directorial project. "We started developing stuff [trying] to figure out the technology. And the luxury [was] that we could try many things."