Leonardo DiCaprio has revealed that Jack Nicholson was the most unpredictable co-star he has ever worked with, describing scenes on the set of Martin Scorsese's 2006 crime thriller The Departed where he genuinely had no idea what Nicholson would do next. DiCaprio, a long-time admirer of Nicholson's work, said the pair "expected the unexpected" while filming together, with the veteran actor's volatile approach ultimately helping DiCaprio inhabit his role as an undercover cop living in constant fear of exposure.

The anecdote centres on an incident after Scorsese suggested to Nicholson that his gangster character should appear more intimidating in scenes shared with DiCaprio. The next day, a prop assistant warned DiCaprio to be cautious, telling him Nicholson had been equipped with a fire extinguisher, a gun, matches and a bottle of whiskey. Although DiCaprio never felt he was in real danger, he said the experience left him with memories he will never forget, and credited Nicholson's unpredictability with sharpening the "24-hour panic attack" quality of his performance in the Oscar-winning film, which also starred Matt Damon, Vera Farmiga, Mark Wahlberg and Alec Baldwin.