Danno, responding to an offer of whiskey from a helicopter pilot played by Jimmy Buffett: "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 James Bond?" Alex O'Loughlin was considered for James Bond before losing out on the part to Daniel Craig.
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 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 vampires.
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".
Fake Brit: Australian actress Clare van der Boom as Danny's British-born ex-wife Rachel.
The art dealer in "Mana'o" is played by Bronson Pinchot, who previously played Balki Bartokomous in Perfect Strangers. And played art dealer/weapons dealer "Serge" in the Beverly Hills Cop series of movies.
Branscombe Richmond, who plays the pirate Saloni in the episode "Powa Maka Moana," well known as Bobby Sixkiller from Renegade.
On the third season episode "Hookman", the double amputee with prosthetic arms is Alex Murphy.
CharlieMurphy also makes an appearance in "Hookman" as one of the amputee's clients.
Yuri Lowenthal and Tara Platt (both otherwise known for their works as VAs), who are a Real Life married couple, are the couple having an affair behind her husband's back in the beginning of "Hoa Pili".
What Could Have Been: 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).