Filming has just begun for the 18th season of NCIS. TV Guide Magazine just revealed that a former cast member will be seen in the new episodes. Mark Harmon's son Sean Harmon will be slipping back into the younger version of his dad's role, "Leroy Gibbs". No one is more fitting for the role of younger "Gibbs".

In the 400th episode of the crime series, we'll see "Gibbs" and the NCIS team and adorable coroner "Donald 'Ducky' Mallard" back investigating. Also, Mark Harmon's eldest son Sean will be back stepping into "Gibb's" shoes!

Meet Mark Harmon's Son Sean Harmon

32-year-old Sean Harmon is one of 69-year-old Mark Harmon and his wife Pam Dawber's sons. Handsome young Sean has been in the film industry for ten years as an actor, stunt coordinator, and stunt double. Sean is also an impressive artist who has posted some of his work on Instagram.

Sean Harmon and Pam Dawber

Sean was first featured in NCIS when he portrayed the younger version of his father during a "Gibbs" flashback. Since then he has been in six episodes as the young version of his dad but has not been seen since the 200th episode special in 2012. Back in June, NCIS producer Frank Cardea told TV Guide Magazine that the 400th episode goal would be "To write a love letter for the long-term fans." His promise has come true with the return of Sean Harmon.