* ActorAllusion:
** In one episode, Gibbs is asked what Ducky looked like when he was younger. He responds, "Illya Kuryakin," who was David [=McCallum=]'s character in ''Series/TheManFromUNCLE'' 40 years earlier. Later proven true in a Ducky flashback in season 12 where Adam Campbell as young Ducky is a dead ringer for [=McCallum=] during that era. Young Ducky even had Illya Kuryakin's turtleneck shirts!
** Gibbs once asked Tony for help with the crossword puzzle clue "TV Drama" and Tony answers "Series/StElsewhere," which Mark Harmon appeared on.
** Tony once says "I've got a better chance of hooking up with Jessica Alba than these guys do of infiltrating Sea Lift." Michael Weatherly was engaged to Jessica Alba for a time. He also starred with her in ''Series/DarkAngel'', where they kept trying to hook up.
*** In the episode ''Obsession'' (7x21), Tony obsesses over a journalist who embodies all what he finds attractive in a woman, and who is missing. When calling her at her cell phone, he says: "It would seem strange, but I feel like I know you". It's not so strange, though: the journalist is played by Ashley Scott, who also played underground operative and potential secondary love interest Asha Barlow in ''Series/DarkAngel''.
** In the Season 4 Halloween episode "Witch Hunt", Abby, in her Creator/MarilynMonroe Halloween Costume, calls Gibbs "Mr. President" in a reference to UsefulNotes/JohnFKennedy. However, Mark Harmon also played the US President in the 2004 film, "Chasing Liberty". That said, Abby was more likely attempting to evoke the time Marilyn sang "Happy Birthday" to JFK.
** Harmon's turn as serial killer Ted Bundy (in the TV movie ''The Deliberate Stranger'') is referenced by Fornell in the episode "Smoked" (4x10).
--->'''Fornell:''' I was on the team that nailed Bundy, Gibbs. And I'm familiar with sick, charming bastards.\\
'''Gibbs:''' That's probably why we get along so well.
** In the season eight double episode "Enemies Foreign/Domestic" (also the name of an episode of ''Series/TheWestWing'' in which Harmon appeared) Tony makes a reference to ''Series/TheWestWing'' by calling [=McGee=] [="McBartlet"=]. Both Mark Harmon and Michael O'Neill (who guest stars in these episodes) played secret service agents on the show.
** A combination of ActorAllusion and ShoutOut: Tony (Mike Weatherly)'s father is played by Robert Wagner. Weatherly met ''NCIS'' producer Donald Bellisario while Weatherly was filming ''The Mystery of Natalie Wood'', in which he played Wood's husband...Robert Wagner.
** In the Episode 'Light Sleeper' while on stake out Tony is reading an entertainment magazine
--->'''Tony:''' Damn, I can't believe this... Mick and Jessica broke up, I'm always the last to know.
:::This is just after Michael Weatherly and Jessica Alba broke up.
** A retroactive one: Early in Season 7, a Metro detective who annoys Gibbs is described as having "tugged on [[WesternAnimation/JusticeLeagueCrisisOnTwoEarths Superman's]] cape".
** In the Season 9 episode "Newborn King", Jimmy Palmer, when explaining that his future father-in-law, Ed Slater, is visiting the NCIS building, he mentions that the first time he learned that Palmer was marrying his daughter, "[Ed Slater] laughed, and then he cried from laughing too hard". Ed Slater is played by Larry Miller, who himself used the phrase "I laughed, I cried" during his first IsThisThingStillOn moment as Principal Jindrake in the movie ''Film/MaxKeeblesBigMove''.
** In season five's "Recoil", Nick Chinlund guest-starred as a detective hunting a serial killer who murdered women and cut off their fingers. Sixteen years earlier, he played Donnie Pfaster on ''Series/TheXFiles'' -- as a serial killer who murdered women and kept their fingers.
** Ziva's codename in "Blowback" is 'Series/DarkAngel'.
** Season 9 introduces Dr. Samantha Ryan (played by Jamie Lee Curtis) as a psychologist and love interest for Gibbs. This is a reference to ''Film/FreakyFriday'' in which she played a psychologist, frustrated with the fact that her unruly teenage daughter refuses to accept her fiance--named Ryan, played by Mark Harmon.
* BackedByThePentagon: The Navy and USMC support the show because malfeasance (regardless of whether it is done by service members or otherwise) is '''always''' brought to justice. In "Child's Play" season 7 episode 9, NCIS Agent Ray, who lost in checkers to the child prodigy, was played by Ray Mabus, the current Secretary of the Navy.
* BeamMeUpScotty: Abby is repeatedly misquoted as having screamed "Stop looking up my skirt!" in "Bloodbath". What she actually says is "And ''don't'' look up my skirt!"
* CastTheExpert:
** Pauley Perrette studied sociology and criminal science before becoming an actress and playing forensic specialist Abby Sciuto.
** An interesting inversion with David [=McCallum=], who knew nothing of pathology when he was cast as Ducky, but developed such an expertise over the years in his studies for the role to make Ducky as spot on to real coroners that the showrunners were considering paying him a consulting fee.
* TheCharacterDiedWithHim: With Ralph Waite dying, Jackson Gibbs died as well. It happened in "Honor Thy Father."
* ColbertBump: Prior to the series airing, real NCIS agents referred to themselves as the [[Creator/RodneyDangerfield Rodney Dangerfields]] of law enforcement because the agency was so obscure they couldn't get any respect. Once the show became a hit, people knew what the agency did and news reports stopped saying "Naval investigators" and actually referring to the agency as "NCIS" or "Naval Criminal Investigative Service".
* {{Defictionalization}}: Theakston's Christmas Ale. Theakston was already a real brewery, but they didn't make a specific Christmas beer - until ''NCIS'' fans started inquiring about it.
* DirectedByCastMember: Michael Weatherly directed season eight episode "One Last Score".
* DyeingForYourArt: Pauley Perrette (Abby) is a natural blonde.
* EditedForSyndication: At least in daytime UK screenings,for gore and violence rather than for timing.
* FakeNationality:
** Coincidentally, the in-series siblings Ziva and Ari. The Israeli Mossad agent Ziva is played by Chilean actress Cote de Pablo, and the Israeli/Palestinian double agent Ari is played by German actor Rudolf Martin.
** Director Thomas Morrow is portrayed by Alan Dale, who is from New Zealand.
* FandomNod: In the season 9 episode "Life Before His Eyes," Gibbs imagines what his life would be like if several things had gone differently. In his alternate timeline, Ziva never came to join NCIS and instead gets arrested for terrorism. Tony is the one to interrogate her, and "guesses" her name wrong several times. One of the names he calls her is "Tiva", which is the online PortmanteauCoupleName given to the Tony/Ziva ship.
* HarpoDoesSomethingFunny: Gibbs simply glaring as other characters have one-sided conversations wasn't something the writers came up with. It was Mark Harmon choosing not to say his lines at all and simply use facial expressions to react to information being given to Gibbs. It quickly became a hallmark of the show and certainly made watching InfoDump scenes a lot more enjoyable.
* HeyItsThatGuy: The main cast have appeared in a lot of other shows. Mark Harmon, Rocky Carroll and Lauren Holly all costarred on ''Series/ChicagoHope''. Harmon was a mainstay on ''Series/StElsewhere''. Carroll had his own sitcom and was the voice of Derek Maza/Talon on ''WesternAnimation/{{Gargoyles}}''. Holly had starring roles in ''DumbAndDumber'' and ''Picket Fences''. Sean Murray was on ''HocusPocus'' and ''Series/{{JAG}}''; he played two different characters in ''Series/{{JAG}}'' so if you count it as being in the same verse as ''NCIS'' it means he's played 3 different characters in the same universe. Michael Weatherly was on ''DarkAngel''. More recently, the actress who played Agent Lee, Liza Lapira, has turned up in ''Series/{{Dollhouse}}'' and ''Series/{{Dexter}}''. After Caitlin Todd died, she morphed into [[Series/RizzoliAndIsles Maura Isles]]. Ducky co-starred in ''Series/TheManFromUNCLE'' as Illya Kuryakin (or as Eric Ashley-Pitt from ''Film/TheGreatEscape''). ''NCIS'''s pilot episode can count as a MythologyGag of sorts, since Ducky at times appears to be the team leader instead of Gibbs, mirroring his prominent role in ''UNCLE''. See also ActorAllusion. Also, although not likely to be brought up in an American show, [=McCallum=] was the Steel half of ''Series/SapphireAndSteel''.
** ''Series/StargateSG1'' fans will wonder about how the SGC intends to get Jonas Quinn off for serial murder in "Skeletons". They might be further confused by Martouf being a dirty Metro cop in "Lost And Found". Master Bra'tac apparently has a double life as elusive ultra-forger Khamal Khakani. Colonel Makepeace appears as an ex-Army colonel running a mercenary band that's hunting Mike Franks' daughter-in-law in a season 7 episode. Valla murders a man who has been killing off her dealers in season 7 episode "Borderland". The late Don S. Davis appeared as a government official in the second season and contributed to one of [=McGee's=] [[CrowningMomentOfAwesome most awesome moments]]. And Jack O'Neill's clone was apparently adopted by a Marine and who was forced to hold a classroom hostage by Mexican drug runners. ''Series/StargateAtlantis'' fans will notice that Michael kidnapped Director Sheppard, and Elizabeth Weir is an overworked ME in "Identity Crisis" and recurs as Ducky's temporary replacement. For the ''Series/StargateUniverse'' fans there's the deceased [[Series/StargateUniverse Gloria Rush]] as the now deceased Lara Macy and [[Series/StargateUniverse Tamara Johansen]] as Dana Arnett from the season 5 episode 'Leap of Faith'.
** One episode had a random teenager played by [[HighSchoolMusical Zac Efron]], in all his feather-headed glory.
** [[Series/TheBill Zain Nadir]] was a Mossad agent who Ziva slept with.
** [[LawAndOrderSpecialVictimsUnit Casey Novak]] as Gibbs' DistaffCounterpart in "Jurisdiction."
** [[Series/{{Supernatural}} Castiel]] accidentally stole a car with an injured, kidnapped woman in it. After he recovered her he [[spoiler:left her to die. ]]. [[Series/{{Castle}} Kevin Ryan]] [[spoiler: was the man who kidnapped her in the first place. This also qualifies as a [[RetroactiveRecognition retroactive]] [[NarrowedItDownToTheGuyIRecognize narrowing it down to the guy you recognize]] ]].
** Is that [[Series/CornerGas Lacey Burrows]] who's the concerned housewife [[spoiler:who did it]]?
** "Caged" even features a minor appearance from Advertising/TheManYourManCouldSmellLike.
** [[Film/IronMan Yinsen]] loses another family member, but doesn't go to see them this time around.
** Gibbs made out (and more) with ''[[Series/StarTrekVoyager Voyager's]]'' Borg Queen!
*** Also, Ducky's true love Margaret Clark is ''[[Movies/StarTrekFistContact]]'' First Contact's Queen as well!
** Anthony [=DiNozzo=] Senior [[AustinPowers regretfully informs Dr. Evil that they have no sharks.]]
** Season 8 had a guest-appears of Alimi Ballard as Special Agent Levin, that is, David from ''{{Numb3rs}}''.
*** Also the Quiz Master from ''{{Sabrina The Teenaged Witch}}''
** The teenager who holds his class hostage with a bomb in Season 3 is [[Literature/{{Twilight}} Mike Newton]].
** [[Series/WhiteCollar Peter Burke]] plays one of Gibb's old friends in "Capitol Offense." He [[spoiler:didn't kill the first person but did help cover the crime up with another killing]]. This one is especially surreal for fans, since the character cheated on his wife, an act which is pretty much as likely to happen on {{Series/White Collar}} as Mozzie making gift baskets for the suits.
** [[Series/DoctorWho River Song]] has apparently taken up black market dealings and flirting with Gibbs.
** Gibb's father? [[Series/TheWaltons John Walton]]. No wonder he's good with a shot.
** And Gibb's namesake "Leroy Jethro" [[Film/TheEmpireStrikesBack ran a cloud-mining facility.]]
** The season 8 episode ''Kill Screen'' shows [[{{Leverage}} Parker]] got into gaming in the world of NCIS instead of thieving.
** [[Series/StarTrekTheNextGeneration Counselor Troi]] is [[spoiler: the director of Mossad following Eli David's death.]]
** Detective Burress in "A Desperate Man" is also [[Series/OneEightHundredMissing AD John Pollock.]]
** [[Film/FreakyFriday2003 Tess and Ryan]] are back together, it seems.
** [[Series/LawAndOrderCriminalIntent Captain Deakins]] is [=McGee=]'s father.
** [[Series/{{Millennium}} Frank Black]] turns up as a sheriff in Season 6.
** [[Series/CriminalMinds Haley Hotchner]] was alive and well in Season 7.
** In "Child's Play" season 7 episode 9, NCIS Agent Ray, who lost in checkers to the child prodigy, [[http://en.wikipedia.org/wiki/Ray_Mabus took a demotion from his day job as]] ''[[http://en.wikipedia.org/wiki/United_States_Secretary_of_the_Navy the real life SecNav]]''.
** [[Series/BabylonFive Delenn]] plays an [[KirksRock Arizona]] artist who accidentally uses radioactive pigments in her paints.
** In season 7, it looks like Agent Doggett of ''Series/TheXFiles'' is still in the military.
** Who knew Melissa Scully (Agent Acully's sister of ''Series/TheXFiles'') would not only survive her death, but marry both Gibbs and Fornell?!
** Hodgins of ''Series/{{Bones}}'' is a toy store manager in an episode in season one.
** Stahma Tarr from ''Series/{{Defiance}}'' was the lead [=ICE=] agent protecting [=SecNav=]'s home in "Semper Fidelis".
* HeyItsThatVoice:
** Did [[Franchise/KingdomHearts Xaldin]] learn to manipulate people during his time in the CIA as Trent Kort?
** [[WesternAnimation/FamilyGuy Peter Griffin's father]] Francis earned a Medal of Honor in the Pacific, it seems.
** "Need To Know" has an MI5 Inspector played by [[VideoGame/MassEffect2 Zaeed Massani]]
** One Season 8 episode features Creator/GeorgeNewbern ([[WesternAnimation/JusticeLeagueUnlimited Superman]][=/=][[VideoGame/FinalFantasyVII Sephiroth]]) as a KnightTemplar {{Western Terrorist|s}}.
** The grief counselor brought in for the aftermath of the season 9 finale/season 10 premiere was [[VideoGame/DragonAgeOrigins Alistair.]]
** Season 10's "Duoble Blind" features [[WesternAnimation/FostersHomeForImaginaryFriends Mac]] as a troubled young petty officer.
* ThePeteBest: Robyn Lively played Special Agent Vivian Blackadder in the two-part ''Series/{{JAG}}'' PoorlyDisguisedPilot. Donald Bellisario reportedly said she was "too soft" for the new show, and she was replaced by Sasha Alexander's Caitlin Todd for the series proper.
* RealLifeRelative:
** Sean Murray, who plays [=McGee=], is the real-life stepson of the show's creator Donald Bellisario.
*** [=McGee=]'s sister is played by his real-life stepsister.
** In one season 9 episode, Abby shows the others a locket containing a picture of her mother. The picture is of Pauley Perrette's real-life (deceased) mother, Donna. The lock of Abby's mother's hair inside the locket was also that of Pauley's mother.
** The young Gibbs is played by Mark Harmon's son Sean.
* SleeperHit: ''NCIS'' is one of the rare examples of a show that's steadily increased its viewing audience as it's gone on, and to continuously do it over a decade is virtually unheard of; nearly every successive season has had an episode that set a new benchmark for the show's viewership[[note]]with only seasons 4 and 5 unable to turn the trick[[/note]], with Season 10's "Shiva" the current record holder at over 22 million viewers.
* TroubledProduction:
** When Donald Bellisario was showrunner, he exercised tight control over the show and continuously rewrote scripts, resulting in pages being delivered just before cameras were supposed to roll and the cast and crew working longer and longer hours because of the resulting delays[[note]]According to Mark Harmon, the cast and crew of [=NCIS=] operated without ever having received a complete script for the first four seasons[[/note]]. This also led to Sasha Alexander leaving the show[[note]]she couldn't handle the thought of having to work 16 hours a day to shoot an entire network TV season[[/note]]. While this isn't unusual in TV production, Mark Harmon finally decided to put his foot down and threatened to quit unless someone else was brought in as showrunner, leading to Bellisario being forced out and Shane Brennan taking over. While this smoothed out the production process (with whole scripts now being delivered 10 days in advance of shooting), Bellisario is now in a messy and ugly legal battle with CBS over royalties that's discouraging the network from pursuing crossover opportunities between the two NCIS series currently on the air.
** When Cote de Pablo's contract ran out after Season 10, she entered into protracted negotiations. While the powers that be said they kept on increasing their offers, de Pablo was hesitant to accept and dragged talks out through the hiatus before deciding to leave a week before production on Season 11 was supposed to start. This left the writers with little time to put together a workable departure for Ziva, including resolving eight seasons worth of UnresolvedSexualTension with Tony, resulting in a rushed two-episode story. Some cast members publicly expressed displeasure at how the actress left (Mark Harmon being particularly backhanded during an appearance on Arsenio Hall).
* WhatCouldHaveBeen: Production notes from the show say that the plan was to develop a romantic relationship between Kate and Tony. Sasha Alexander's decision to leave the show after two seasons prevented that potential arc from happening. It's touched upon in the show's 200th episode where, in an alternate reality, Tony and Kate marry and start a family while Kate continues to be exasperated at Tony.
* YouLookFamiliar:
** Joe Spano played a Navy captain in ''{{JAG}}'' before turning up as Fornell on its spinoff.
** Also, Sean Murray played two different characters in ''{{JAG}}'' before [=McGee=].
** Terry O'Quinn played long term returning character Admiral Boone in ''{{JAG}}'' and would go onto play Joe White in the remake ''Hawaii Five-0'' which is also in the same verse.


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