A Complete Unknown director James Mangold explains why Johnny Cash appears in his Bob Dylan biopic, despite having told his story in Walk the Line.

As shown in A Complete Unknown, singers Bob Dylan and Johnny Cash created a friendship in real life, but some true details are altered or left out.

The filmmaker first tackled the life of Johnny Cash in 2005's Walk the Line, which garnered tons of acclaim, including an Oscar win for Reese Witherspoon and a nomination for Joaquin Phoenix. Now, Mangold returns to Cash in A Complete Unknown, another musical biopic, this time centered on the rise of a young Bob Dylan ( Timothée Chalamet ).