* 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 while Scott Caan has been put into a waiter's uniform more often than not in Film/OceansEleven and the sequels.
** [[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 "[[Recap/HawaiiFive0S03E15 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]].
** Meeting a cop from San Francisco, Jerry remarks "more than one person escaped from Alcatraz," which is funnier considering Jorge Garcia's role on the ''Series/{{Alcatraz}}'' show.
** Aunt Deb spent the majority of her life in Los Angeles and is a talented singer, just like her actress, Creator/CarolBurnett.
* ActorSharedBackground: Lou Grover grew up in Chicago, as did his actor Chi [=McBride=].
* {{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.
* 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.
** Daniel Baldwin plays Paul Delaney in season 3, brother of Frank Delaney played by William Baldwin.
* RealLifeWritesThePlot:
** Scott Caan injured his knee in Season 1, leading them to writing in a knee injury for Danny.
** Alex O'Loughlin had problems with addiction to pain meds. For the episodes filmed while he was in treatment, [=McGarrett=] was said to be away from the islands tracking down Joe White.
** Grace Park was on maternity leave during the fourth season, which is why she was absent from several episodes. For such episodes, Kono was with her boyfriend Adam on the run from the Yakuza.
** Scott Caan became a father in July 2014, his wife and newborn ended up staying in California (not Hawaii where the show's filmed), so he's missing from several episodes during subsequent seasons because of this.
* 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).