Former The OC actor on crusade to take down 'stupid' cryptocurrency

For many millennials, Ben McKenzie is still best known for his role as a troubled teen from the wrong side of the tracks who was adopted by the wealthy Cohen family.

The now 47-year-old actor noted as much in the US Congress, when he appeared before its Senate Committee on Banking four years ago.

"You can also call me Ryan Atwood from The OC," he quipped.

McKenzie's appearance before the committee highlights the career swerve the Hollywood actor has made since appearing in television shows such as The OC and Gotham.

He is now drawing on his undergraduate studies in economics to publicly criticise one of the most headline-making financial movements of the past decade.

"In my opinion, the cryptocurrency industry represents the largest Ponzi scheme in history," he told the US Senate.

Speaking to ABC News, McKenzie explains how he became a crypto cynic and why he has just put out a documentary openly calling the movement "stupid".

The star and director made the film as a follow to the book on cryptocurrency that he wrote with journalist Jacob Silverman.

"I had a lot of impostor syndrome about playing this role of investigative journalist," he tells ABC News about making a feature film.

"That's clearly not my training."