The popular CBS series NCIS has apparently bid farewell to its last original cast member after a staggering 22 seasons.

The show's writers have smoothly transitioned out the final founding cast members by introducing their successors.

The crime drama has consistently delivered impressive ratings for over two decades, which is why the series, created by Don Belissario and Don McGill, continues to thrive since its debut in 2003.

Over the course of NCIS' run, numerous characters have made their exit.

However, the CBS show's top brass have continually introduced fresh faces to maintain the much-loved narrative, regardless of previous actors departing the series.

Following the death of NCIS star David McCallum last year, which led to his character Ducky Mallard being written out of the show, almost no original characters remain, as reported by Screen Rant.

Currently, actor Timothy McGee holds the record as the longest-serving NCIS star, but another character from the series' first-ever episode, Yankee White, has just effectively been written out.

Beyond the primary cast, actor Joe Spano, known for his role as recurring character Tobias Fornell, has been a part of NCIS since its inaugural episode.

He quickly became a fan favourite, representing the FBI within the NCIS universe, with his most recent appearance in the 1000th episode of NCIS earlier this year.

However, the series may have abandoned his character after bringing back a new FBI representative in a recent episode, Sticks and Stones.

Deputy Director Wayne Sweeney (played by Erik Passoja) has a history with the team's new Special Agent in Charge, Alden Parker (Gary Cole) and could be the show's new face of the FBI going forward, potentially leaving no room for Gibbs' (Mark Harmon) old ally.

It remains uncertain whether Spano will make a comeback to NCIS. At present, it appears doubtful.

Despite the alterations to NCIS, there are more transformations occurring within the NCIS universe. Currently under development is the spinoff, NCIS: Tony and Ziva.

Die-hard fans of the series will remember the playful banter between agents Tony DiNozzo (Michael Weatherly) and Ziva David (Cote de Pablo) from the early seasons.

After their departure from the original series, they reunited off-screen in Paris. Reprising their roles in the new NCIS series as Tony DiNozzo and Ziva David are the show's original stars, Michael Weatherly and Cote de Pablo.

Weatherly has been a part of NCIS since the first episode, while de Pablo was introduced in the premiere of season three following the murder of Agent Kate Todd (Sasha Alexander).

NCIS season 22 continues Mondays on CBS in the US and is available to stream on Disney+ in the UK.