Washington D.C., July 16 -- : Actor Leonardo DiCaprio has left his co-stars Brad Pitt and Margot Robbie really impressed during the filming of Quentin Tarantino's 'Once Upon a Time in Hollywood'.

In the highly-anticipated movie, set in Los Angeles in 1969, DiCaprio portrays a fading TV actor Rick Dalton, who is trying to keep his career alive. In one of the scenes showcased in the trailer, DiCaprio is seen having an emotional breakdown, which was actually improvised and left his co-stars in awe of the actor, reported E! News.

"That was all improvised and wasn't written in the script," Tarantino told Today's Harry Smith during a joint interview with DiCaprio, Pitt, and Robbie.

Pitt, who plays Dalton's stunt double Cliff Booth, seemed very...