Bernard, who plays TONY ALMEIDA in the hit drama series, thought it would be funny to report Kirshner as a marijuana user to cop pals and have them arrest her on the set.
But Kirshner and producers weren't laughing when the police officers took the practical joke too far and insisted the actress accompany them to their local station.
Bernard then staged a fake fight with the cops, which left Kirshner distraught and unable to film scenes with her joker co-star for hours.
The actor recalls, "The whole day was made up of scenes between Mia and me, which meant a lot of money lost, so the producers were kind of losing it... Our director almost had a heart attack. It was a fun day at the office."
But 24 star Kiefer Sutherland was among those who didn't see the funny side of the prank.
He adds, "He (Bernard) had two police officers arrest Mia Kirshner for allegedly smoking marijuana outside her dressing room.
"As they went to take her away, Carlos got in a fight with the two officers about what he thought they should be doing in protecting the city. The director stepped in to separate Carlos from the police, and he really did lose it."
The cameras rolled as the prank went wild and now cast and crew have the whole drama on film.
A set source says, "Mia was shaken up at the time but I think she's sees the funny side of her arrest now, and, for the record, she doesn't smoke pot on the set."