Suggestions by @siddarthsid

Harry Connick Jr.

as Robert Serber in Oppenheimer (2003)

Nathan Fillion

as Seth Neddermeyer in Oppenheimer (2003)

Steven Spielberg

as Director in Oppenheimer (2003)

William Sadler

as Roger Robb in Oppenheimer (2003)

Giovanni Ribisi

as Frank Oppenheimer in Oppenheimer (2003)

David Schwimmer

as Kenneth Bainbridge in Oppenheimer (2003)

James Cromwell

as Vannevar Bush in Oppenheimer (2003)

Anthony Hopkins

as Niels Bohr in Oppenheimer (2003)

Gary Sinise

as Colonel Boris Pash in Oppenheimer (2003)

Jack Nicholson

as President Harry S. Truman in Oppenheimer (2003)

Peter Ustinov

as Albert Einstein in Oppenheimer (2003)

Val Kilmer

as Ernest Lawrence in Oppenheimer (2003)

Cameron Crowe

as Edward Teller in Oppenheimer (2003)

Kate Winslet

as Jean Tatlock in Oppenheimer (2003)

Alfred Molina

as Isidor Isaac Rabi in Oppenheimer (2003)

Tom Hanks

as Gen. Leslie Groves in Oppenheimer (2003)

Kevin Kline

as Lewis Strauss in Oppenheimer (2003)

Michelle Pfeiffer

as Katherine Oppenheimer in Oppenheimer (2003)

Daniel Day-Lewis

as J. Robert Oppenheimer in Oppenheimer (2003)

John Hurt

as V in V for Vendetta (1975)