The evolving dramatic universe centered around "NCIS" is hitting a major milestone: 1,000 combined episodes.

The April 15 episode of the original "NCIS" (9 EDT/PDT) will reach the millennial mark propelled by the "NCISverse" of shows that now spans from "NCIS: Hawaii" to "NCIS: Sydney," on CBS and Paramount+. Franchise stars from past and present were on hand for a February celebration during the filming of the episode, which features crossover stars Daniela Ruah (from now-defunct "NCIS: Los Angeles") and Vanessa Lachey (from "NCIS: Hawaii").

Two new upcoming shows – "NCIS: Origins" and the still-untitled spinoff led by Michael Weatherly and Cote de Pablo – were also represented at the party.

"Now it's like our own Marvel universe within 'NCIS,' which is the ultimate testament of the power of this show," says Rocky Carroll, who has portrayed Leon Vance on "NCIS" since 2008.

As CBS celebrates the achievement with an hourlong "Entertainment Tonight" special "NCISverse: The First 1,000" (Monday, 9 EDT/PDT), here's the state of TV's super franchise centered around the once little-known Naval Criminal Investigative Service:

'NCIS' (2003 - )

"NCIS," also known as "The Mothership," is a spinoff of creator Donald Bellisario's naval legal show "JAG," which aired on NBC in 1995-96 and for nine more seasons (1997-2005) on CBS. 

Notable characters: Mark Harmon, the "NCIS" cornerstone as Leroy Jethro Gibbs, left in 2021 after nearly two decades. Other departed original characters include Weatherly's Anthony "Tony" DiNozzo, who departed in 2016 after 13 seasons, Pauley Perrette's Abby Sciuto, exiting in 2018 after 350 episodes, and David McCallum's Donald "Ducky" Mallard (the veteran actor died last year).

"NCIS" has been network TV's most-watched drama for the last five seasons with a team that includes Carroll, Sean Murray (Timothy McGee), Brian Dietzen (Jimmy Palmer), Wilmer Valderrama (Nicholas Torres), Katrina Law (Jessica Knight), Diona Reasonover (Kasie Hines) and Gary Cole (Alden Parker).

Seasons: 21

How to watch: CBS (Mondays 9 EDT/PDT); Paramount+; Netflix (first 15 seasons).

Flavor: This is the "The Mothership." After the 1000th celebration, the "NCIS" cast went right back to work filming. "That typified the reason for our longevity," says Carroll. "It's like, we're still relevant, still an immensely popular show. and we still got an episode to crank out."

'NCIS: Los Angeles' (2009-23)

Notable characters: Ruah's Kensi Blye and the star pairing of Chris O'Donnell and LL Cool J, as G. Callen and Sam Hanna, respectively. Linda Hunt starred as Henrietta "Hetty" Lange and Eric Christian Olsen as Marty Deeks.

Seasons: 14

How to watch: PlutoTV, for purchase on iTunes.

Flavor: The first spinoff was an instant hit that played a crucial role in expanding the franchise "during its incredibly long run," says David Stapf, president of producer CBS Studios.

'NCIS: New Orleans' (2014-21)

Notable characters: Scott Bakula as Dwayne "King" Pride, CCH Pounder as Loretta Wade and Lucas Black as Christopher LaSalle.

Seasons: 7

How to watch: Paramount+, PlutoTV.

Flavor: The first Southern field office had all the gritty crime-solving in The Big Easy with only-in-NOLA musical moments that included Bakula really playing the piano as King.

'NCIS: Hawai'i' (2021- )

Notable characters: Lachey became the franchise's first female and Asian American, lead as Special Agent in Charge Jane Tennant of the Pearl Harbor Field Office. Supporting stars include Alex Tarrant (Kai Holman), Noah Mills (Jesse Boone), Jason Antoon (Ernie Malik), Tori Anderson (Kate Whistler) and Yasmine Al-Bustami (Lucy Tara). Sam, LL Cool J's LA transplant, moved to "NCIS: Hawai'i" in Season 3.

Seasons: 3

How to watch: CBS (Mondays at 10 EDT/PDT), Paramount+.

Flavor: Set in paradise with unforgettable island surroundings and many crimes intertwined with Hawaiian lore – with an added dose of Cool J. Stapf says the actor will continue "hopefully, forever, or as long as he wants to do it."

'NCIS: Sydney' (2023- )

Notable characters: Michelle Mackey (Olivia Swann) heads the collaboration between the NCIS Sydney office and the Australian Federal Police led by Jim "JD" Dempsey (Todd Lasance). Originally conceived for Australian TV audiences but recruited to the American schedule during the Hollywood strike, "NCIS: Sydney" has proven its worth, fair dinkum, and was renewed for a second season in March.

Seasons: 1

How to watch:Paramount+

Flavor: The first international spinoff, set near the iconic Sydney Harbor bridge, embraces U.S.-Aussie cultural differences while still solving crimes. "In divisive times, it's wish-fulfillment," says Stapf.

'NCIS: Origins' (CBS 2024-25)

Notable characters: Beloved leader Gibbs returns as a younger man for the franchise's prequel series, "NCIS: Origins," announced in March "The Hating Game" star Austin Stowell will play young Gibbs. "We weren't just casting Gibbs; we were casting a young Mark Harmon," says Stapf. "And Austin embodies it all."

Harmon, 72, will narrate and serve as executive producer. Sean Harmon, Mark's real-life son, who often played the younger version of Gibbs in flashbacks on "NCIS," will also serve as executive producer.

"Origins" follows young Gibbs as he fights for his place on the team led by NCIS legend Mike Franks. Kyle Schmid has been cast as the younger version of the Texan Franks (Muse Watson in "NCIS") who played a pivotal role in Gibbs' early career.

How to watch: Coming to CBS this fall.

Flavor: Only part Harmon. But the next chapter of a beloved "NCIS" character that launched a franchise.

Untitled Tony and Ziva spinoff (CBS)

Notable characters: Fans loved the special sizzle between agents Tony DiNozzo (Weatherly) and Ziva David (Cote De Pablo, who left "NCIS" in 2013 after eight seasons). The couple, known as Tiva, announced their return in February for a European-set spinoff on Paramount+. No premiere date has been set, nor has an actor been cast to play the couple's young daughter Tali.

After Tony’s security company is attacked by terrorists, the new show features a family on the run through Europe.

How to watch: Coming to Paramount+

Flavor: Whatever the title, it's "NCIS: Tiva." In a statement, the two stars promised "an action-packed roller coaster fueled by love, danger, tears and laughter."