* ActorAllusion:
** Danno, responding to an offer of whiskey from a helicopter pilot played by Music/JimmyBuffett: "I'm more of a margarita guy myself."
** Undercover, dressed up as players at an illegal casino, Danno asks Steve, "How come I look like a waiter and you look like Film/JamesBond?" Alex O'Loughlin was considered for James Bond before losing out on the part to Daniel Craig.
** [[Creator/MasiOka Max]] begins an episode talking about the plausibility of time-travel. In another episode, he asks an ICE agent (played by Greg Grunberg) if they've met before. Both were on ''Series/{{Heroes}}''.
** Danno, played by Scott Caan, refers to a suspect, played by his father James Caan, as "old man."
** In one episode, Steve opens a fridge to find it filled with bottles of blood. Danny jokes that it is for [[Series/{{Moonlight}} vampires]].
** [[Series/{{Lost}} John Locke]] is pals with [[Series/{{Lost}} Jin]] again.
** Creator/PeterWeller guest stars in the episode "Hookman" as a sniper with [[Franchise/RoboCop prosthetic hands]].
** When Creator/DanteBasco plays a criminal, his WeaponOfChoice is a flamethrower. He provided the voice of two [[WesternAnimation/AvatarTheLastAirbender fire]][[WesternAnimation/TheLegendOfKorra benders]].
* {{Defictionalization}}: A throwaway reference to "Kukui High School" in the pilot has led to fans [[http://www.hawaiinewsnow.com/Global/story.asp?S=13227331 creating]] a whole [[http://www.staradvertiser.com/columnists/20100926_five_0_artistic_license_spurs_offshoots_online.html backstory]] for an otherwise fictional school, complete with [[http://www.kukuihigh.com/logo-shop/ logo wear.]] In Hawaii, high schools are a big deal.
* UsefulNotes/AmericanAccents:
** Hawaii's pidgin English (officially "Hawaii Creole English") features in most episodes, as spoken by various minor characters. [=McGarrett=], Kono, and Chin Ho all understand and can also speak it -- to the confusion of Danno, the only member of the Five-0 team not born and reared in Hawaii. Even when not speaking purely in Pidgin, [=McGarrett=], Kono, and Chin Ho often use da Pidgin kine expressions and phrases, brah.
--->'''Surfer:''' Ho, brah, where you eat it?\\
'''Danno:''' I'm sorry, what?\\
'''Surfer:''' Da kine, brah.\\
'''Danno:''' I'm sorry, are you speaking English?\\
'''Surfer:''' Hey no need for get agro.\\
'''[=McGarrett=]:''' He caught it on land, brah... Danno don't surf.\\
'''Surfer:''' Shoots.\\
'''Danno:''' I dare you to tell me what he just said.
** Danno has a very strong {{Joisey}} accent, which is pretty accurate for the region he claims to be from.
** Steve's Tough Guy accent shades into some kind of New York/Joisey hybrid sometimes, even though he's from Hawaii. Maybe his Australian actor imprinted on Scott Caan?
* FakeAmerican:
** Alex O'Loughlin. When in character as Steve [=McGarrett=], he sounds just like an American; when out of character (such as when being interviewed or doing promotional appearances) his Australian accent is unmistakable. Yet again, Steve's American accent is almost too pretty to be real.
** Also, Korean-Canadian Grace Park as Kono. But do know that Grace also has American citizenship, since the Canadian government does allow dual citizenship. So it may not be totally true.
** Tony Curran as a Boston-born Irish mob hitman in "Ike Maka".
* FakeBrit: Australian actress Clare van der Boom as Danny's British-born ex-wife Rachel.
* HeyItsThatGuy:
** The Hesse brothers, a.k.a. [[Series/BuffyTheVampireSlayer Spike]]/[[{{Series/Torchwood}} John Hart]] and [[Film/TheBoondockSaints Murphy MacManus]]/[[{{Series/TheWalkingDead}} Daryl Dixon]].
** [=McGarrett=] Senior, played by perennial H!ITG Creator/WilliamSadler(the father from ''Film/TheGreenMile'', Sheriff Valenti from ''Series/{{Roswell}}'').
** Not to mention [[Series/{{Moonlight}} Mick St. John]], [[Film/OceansEleven Turk]], [[Series/{{Lost}} Jin-Soo Kwon]] and [[Series/BattlestarGalactica2003 Boomer/Athena]] have all become Hawaii state cops.
** [[Series/{{Heroes}} Hiro Nakamura]] is also a [[http://www.cbs.com/forum/posts/list/0/133958.page coroner.]]
** [[Series/TwentyFour Martha Logan]] went from First Lady to Governor of Hawaii.
** [[Series/SonsOfAnarchy Cherry]] is [=McGarret=]'s sister.
** [[Series/HerculesTheLegendaryJourneys Hercules]] is a CorruptCorporateExecutive.
** [[Series/LawAndOrderSpecialVictimsUnit Detective Chester Lake]] as a rogue Navy SEAL.
** [[Film/XMen Lady Deathstrike]] as the Governor's new public safety aide.
** [[Series/HomicideLifeOnTheStreet Bayliss]] tragically loses a daughter to murder. [[Series/VeronicaMars Again]].
** [[Series/{{CSINY}} Flack's girlfriend]] is now an assassin.
** [[Series/TwentyFour Tony's late wife]] is now Chin's [[spoiler:late ]]wife as well. And Tony himself is now an FBI agent in charge of the Witness Relocation Program.
** [[Film/TenThingsIHateAboutYou Bianca Stratford]]/[[TheSecretWorldOfAlexMack Alex Mack]] is a CIA agent on leave investigating Wo Fat.
** Speaking of [[IronChefAmerica Wo Fat]]...
** Grace Barry is Danno's ex-wife.
** [[Series/{{Lost}} John Locke]] is Steve's mentor.
** [[Series/CriminalMinds Haley Hotchner]] is the fugitive wife of a dead embezzler.
** Music/JimmyBuffett is the helicopter pilot, which is a ShoutOut to one of his hobbies.
** [[spoiler:The art dealer in "Mana'o" is played by Bronson Pinchot, who previously played Balki Bartokomous in ''Series/PerfectStrangers''. And played art dealer/weapons dealer "Serge" in the ''Film/BeverlyHillsCop'' series of movies.]]
** [[spoiler: Branscombe Richmond, who plays the pirate Saloni in the episode "Powa Maka Moana," well known as Bobby Sixkiller from ''Series/{{Renegade}}''.]]
** One of the Irish mobsters, John O'Toole in "Ike Maka" was Creator/VincentVanGogh in ''Series/DoctorWho''.
** Phillies outfielder Shane Victorino and Olympic gold medalist Apolo Ohno both show up in "Kupale", the latter as a suspect.
** [[Series/TheEvent Vicki]] was Hilary Chaver, the hitwoman in "Ua Hala", the second season finale.
** And Adam Noshimori was also once [[Series/TheEvent Simon Lee]].
** [[Franchise/MassEffect Admiral Anderson]] is mob boss Jimmy Cannon.
** On the third season episode "Hookman", the double amputee with prosthetic arms is [[Franchise/RoboCop Alex Murphy]].
** [[Series/ChappellesShow Charlie]] [[WesternAnimation/TheBoondocks Murphy]] also makes an appearance in "Hookman" as one of the amputee's clients.
** Creator/YuriLowenthal and Creator/TaraPlatt (both otherwise known for their works as [=VAs=]), who are a RealLife married couple, are the couple having an affair behind her husband's back in the beginning of "Hoa Pili".
** Music/HenryRollins (of ''Series/SonsOfAnarchy''[=/=]Music/BlackFlag fame) plays a child abductor in "Ho'opio".
** [[Series/BreakingBad Badger]] is a computer technician in "Kapu". He even [[TooDumbToLive waves his bong at Danno]].
** [[Series/ChildrensHospital Dr. Blake Downs]] appears in the high school reunion episode. He was Chin Ho's lab partner, and a bigshot bully to Jerry.
** [[Series/BattlestarGalactica2003 Sharon Valerii]] is Kono.
** [[Film/TheExpendables Toll Road]] is now an arsonist.
* HeyItsThatVoice: Holy... ''[[WesternAnimation/{{Gargoyles}} Goliath]]''/''[[VideoGame/ModernWarfare Foley]]'' is a gangster who put a hit on a federal agent?!
** Also, apparently [[VideoGame/SaintsRow Johnny Gat]] became a cop.
* PlayingAgainstType: [[Series/{{Glee}} Coach Tanaka]] as a Filipino terrorist.
* RealLifeRelative: Creator/JamesCaan (father of Scott) guest starred in "Lekio" as a former cop/murder suspect.
* WhatCouldHaveBeen: Reportedly James [=McArthur=] (the original show's Danny) was set to play Danny's father in the remake when he unexpectedly died. The role was actually Mamo Kahike, which was eventually played by Al Harrington (making him the first regular from the original show to appear).