'NCIS' 1000th Episode: Go Behind the Scenes as Cast Teases Easter Eggs, Crossovers and More (Exclusive)

The show will air its 1000th episode in the franchise on Monday night.

NCIS is celebrating 1,000 episodes by doing what the franchise does best -- bring people together. 

On Monday night, the long-running CBS series will air its 1000th episode in the franchise more than two decades after first hitting the airwaves. In the 21 years since the pilot aired in September 2003, the show has amassed an unmatched fanbase, created 4.2 trillion minutes of television and spawned several wildly successful spinoffs based in Los Angeles, Hawaii, Sydney and New Orleans. 

While the mothership is ostensibly the most triumphant of the bunch -- racking up nearly half of the 1,000 episodes franchise-wide -- fans have become equally attached to the various series set around the world and the lovable characters each show brings. 

Gary Cole, Katrina Law, Rocky Carroll, Sean Murray, Brian Dietzen, Wilmer Valderrama, Diona Reasonover, and Chris O'Donnell celebrate 1000 episodes of 'NCIS' - Getty Images

In celebration of the major milestone, ET was recently on set to mark the victorious moment for NCIS and CBS and spoke with cast members from all five shows, who teased what is to come in the highly anticipated special episode, which airs on Monday at 9 p.m. ET.

"We'll get to see my character, McGee, in a position that we have never seen him in, in 20 years. I'll give you that much," NCIS mothership star Sean Murray said. "If I attach anything else to it then I give it away."

The 46-year-old actor has played Special Agent Timothy McGee since the show's inception and told ET that while the 1000th episode will be fun to watch for any and all fans, the OG lovers are going to be the most pleased by what the cast and crew bring to the table. 

Brian Dietzen as Jimmy Palmer and Sean Murray as Special Agent Timothy McGee in 'NCIS' - CBS via Getty Images

"If you're like an old school fan of the show, tried and true, you're gonna have some real cool Easter eggs and some really interesting, fun things to see in the 1000th episode," Murray said. "We're not just letting it go by as one of our regular episodes, you know what I mean?"

He also teased some possible cameos from NCIS cast members and friends of past years. While Murray did not specify any names, it's safe to say fans are crossing their fingers for a Mark Harmon appearance after his departure in 2023. Also on the table are fan faves Cote de Pablo and Michael Weatherly, who were recently announced to be getting their own 10-episode spinoff

Michael Weatherly and Cote de Pablo on 'NCIS' - CBS

Elsewhere on set, Wilmer Valderrama -- an NCIS star who has also appeared on NCIS: Hawaii and NCIS: Los Angeles as Nick Torres -- shared that the filming of the 1000th episode was special for many reasons but particularly because it brought together the cast and crews from across the franchise. 

"It's so cool to see all the shows come together to celebrate today," Valderrama, 44, said. "This is their win as [much as] anyone else’s, you know?"

He added, "Everyone has contributed to these 1,000 episodes -- seeing their faces and seeing how proud they are to be here, I think that's also something that we are definitely gonna remember."

Katrina Law, Wilmer Valderrama, Sean Murray and Gary Cole in 'NCIS's 100th episode - Getty Images

"[It's] just fun to celebrate the 1000th," NCIS: Los Angeles star Chris O’Donnell said. "We had 14 wonderful years as we spent time obviously on this set, we were launched out of this show, we came back, did crossovers, so it's big, you know? The extended family is real."

O'Donnell's iteration wrapped in 2023 after contributing more than 320 episodes to the franchise's total count. The series also starred LL Cool J, Daniela Ruah, Linda Hunt and Renée Felice Smith.

"We're part of TV history, it's something to be proud of for sure," O'Donnell continued. "I'm very proud of the 14 years we did on our show... it's amazing."

'NCIS: Los Angeles' cast members during their March 2023 wrap party after 14 seasons - Getty Images

The 1000th episode of NCIS airs on Monday, April 15, at 9 p.m. ET. 

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