Robert Downey Jr. Calls Cillian Murphy's Oppenheimer Transformation BANANAS (Exclusive)

Robert Downey Jr. gushes to ET's Will Marfuggi about co-star Cillian Murphy's transformation into J. Robert Oppenheimer for their upcoming film, 'Oppenheimer,' a biopic about the man credited with creating the atomic bomb. 'Oppenheimer,' in theaters on July 21.