Miami Vice by Michael Mann

Michael Mann had his actors train with real-life undercover law enforcement officers. Both Jamie Foxx and Colin Farrell observed undercover operations from a safe distance. Colin Farrell was told he'd learned so much, he was welcome to participate in a real sting operation.

After suffering anxiety and insomnia that night, Farrell contacted the agent-in-charge and was told that the sting operation was staged and that Farrell was never in any danger; he was to be told the next morning during a debrief.