"NCIS" has been hit by some big departures in recent years but one actor that has stayed loyal is Sean Murray.

The 38-year-old has played Special Agent Timothy McGee on the naval drama since its 2003 debut and says he isn’t going anywhere.

Cote de Pablo, popular as former Mossad agent Ziva David, quit "NCIS" in 2013. Emily Wickersham joined the cast as probationary agent Ellie Bishop to cover the loss.

A fortnight ago Michael Weatherly, who has played special agent Tony DiNozzo since the start, announced that he is leaving at season’s end.

Mark Harmon, Pauley Perrette, and David McCallum, along with Murray, will be the only original cast members left on the show.

“It has been a wonderful ride so far,” Murray says. “Timothy McGee was unlike any character I had ever played before but I had a very clear idea of who he was.

“What has kept it interesting for me is that there has been a progression in all the characters on the show over the years, and McGee more than anyone.”

In Season one, McGee had a relationship with forensic specialist Abby Sciuto (Perrette). Later he began dating cryptologist Delilah Fielding (Margo Harshman).

Starting as a junior field agent led to a lot of teasing from DiNozzo. McGee has also had his issues with supervisor Leroy Gibbs (Harmon).

“McGee was only meant to join the team for a few episodes but it just felt right — like a missing piece to the pie.

“I came back and did a big scene with Michael and you could start to feel the sort of rapport that Timothy and Tony would eventually build. Tony’s like the crazy older brother and McGee’s like the prudish younger brother.”

"NCIS" is into its 13th season and shows no sign of losing popularity. Recent episodes have averaged more than 22 million viewers.

“The beauty of 'NCIS' is that all the characters are a little different,” Murray says. “Because the show has run so long we’ve really gotten to explore that stuff a lot.

“When we first saw McGee he had a lot to learn. He was tech-savvy but he wasn’t street smart in any way.”

Murray started acting in his teens and built up a string of credits, including "NCIS" forerunner "Jag" as well as movies "Hocus Pocus" and "This Boy’s Life," before 2003.

“When I first worked with Mark Harmon I was 15 years old on 'Harts of the West,'” Murray recalls. “He had a pretty heavy guest role as a drunken rodeo clown in our second or third episode.

“Mark and I have similar work ethics. I’ve learned a tremendous amount from him over the years — about being an actor, about being part of the business.

“From the beginning we have all taken on more responsibility. You’re not just an actor. We all contribute ideas, we are very involved in our characters. We are all so close.”

This article originally appeared on News.com.au.