The Fifth Man (4×03) guest stars

©CBS

Without question, the Oct. 9 episode of NCIS: L.A. is the mother of all mysteries.

While the team tracks down a suspect in a casino, four women – portrayed by the lead actors’ real-life mothers – are playing poker.

When executive producer Shane Brennan e-mailed the CBS drama’s stars with the idea, “I thought it was a joke,” Chris O’Donnell says. “When I found out he was serious, I was excited to call my mom. I knew this would be the biggest deal for her.”

It was a thrill for the actors as well. “It was fun getting to work and seeing her in hair and makeup,” Eric Christian Olsen says of having his mother, Jeanne, on-set.

[Read the whole article on people.com]