Sean Penn is in negotiations to star in 'The Secret Life of Walter Mitty'.

The 'Milk' actor looks set to appear opposite Ben Stiller in the fantasy-comedy movie - a remake of the 1947 Danny Kaye film based on James Thurber's short story - as he is being lined up for a small supporting role in the 20th Century Fox production.

Ben is directing the film as well as starring in the lead role as a timid magazine photo manager, who dreams of going on an adventure before finding himself involved in one when he goes in search of a missing negative, Deadline reports.

'Bridesmaids' star Kristen Wiig has been lined up to play the dream girl of Ben's alter-ego, and Adam Scott, Shirley Maclaine and Patton Oswalt are also set to appear in the production.

Sean recently finished filming crime movie 'The Gangster Squad' - which stars Emma Stone, Josh Brolin and Ryan Gosling - which sees him play Los Angeles gangster Mickey Cohen.

The 51-year-old star has recently been seen in the Paolo Sorrentino-directed 'This Must Be The Place' and 2011 motion picture 'The Tree of Life' opposite Brad Pitt and Jessica Chastain.