A quartet of long established "NCIS" stars have signed on for at least two more seasons with TV's most watched drama series.

Pauley Perrette (Abby Sciuto), Rocky Carroll (Leon Vance), Sean Murray (Tim McGee) and David McCallum (Donald "Ducky" Mallard) have all inked new deals for seasons 14 and 15.

Michael Weatherly Exits Stage Left

News of the signings comes just weeks after original cast member Michael Weatherly (Agent Tony DiNozzo) made his last appearance on the show, making the choice to exit the cast to pursue other interests.

Fellow original cast member Mark Harmon (Agent Leroy Jethro Gibbs) signed on for two more seasons back in February.

Series showrunner Gary Glasberg recently talked about moving on without the likeable DiNozzo, telling reporters, "Michael is and was a huge part of our family behind the scenes but everybody wishes him well with this huge opportunity he has. And we welcome some new people and the great guests that we'll continue to have. We'll show up for work come July and start all over again."

Wilmer Valderrama Joins mix

Already show execs have announced former "That 70s Show" star Wilmer Valderrama will be joining the cast next season, playing the role of a field agent returning from a deep cover assignment.

At the end of last season, FBI agent Tess Monroe (played by Sarah Clarke) and MI-6 agent Clayton Reeves (played by Duane Henry) joined the cast in regular, recurring roles.

The series is also rumored to be seeking to cast the role of a new female regular. Meanwhile, Weatherly has signed on to star in the new CBS aired drama series "Bull."

During Season 13, "NCIS" averaged 20.54 million viewers for first-run episodes. The series has spawned such network spin-offs as "NCIS LA" and "NCIS New Orleans."

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