"Book 'em, Danno." It’s arguably the most famous catchphrase in television history. Even if you’ve never seen a single frame of the show, you know the line. But when people ask who played Danno on Hawaii Five-0, the answer depends entirely on which generation of TV you grew up with. You’re either thinking of the stoic, classic cool of James MacArthur from the original 1968 run, or you’re picturing the high-energy, "carguments"-prone Scott Caan from the 2010 reboot. Both men took a character that could have been a simple sidekick and turned him into the emotional heartbeat of the series.
It’s wild how one name can represent two completely different eras of masculinity and television style.
The Original Danny Williams: James MacArthur’s Legacy
James MacArthur wasn’t actually the first choice for Danny Williams. In the original 1967 pilot, the role was played by Tim O'Kelly. But testing showed he didn't quite have the chemistry needed with Jack Lord’s Steve McGarrett. So, the producers brought in MacArthur. He stayed for eleven seasons. Think about that. Eleven years of playing the dependable, straight-laced second-in-command.
MacArthur brought a specific kind of "Old Hollywood" gravitas to the role. He was the son of legendary actress Helen Hayes and playwright Charles MacArthur, so acting was basically in his DNA. On screen, his Danno was the perfect foil to McGarrett’s often cold and rigid leadership. While McGarrett was the unstoppable force, MacArthur’s Danno was the guy who kept things grounded. He was relatable. He was the guy doing the legwork, the guy you trusted.
By the time 1979 rolled around, MacArthur decided he’d had enough. He felt the character had hit a ceiling and the scripts were getting a bit repetitive. He famously skipped the final season, which many fans feel left a void the show couldn't quite fill before it finally went off the air in 1980.
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The 2010 Reimagining: How Scott Caan Changed Everything
When CBS announced they were rebooting the show in 2010, the big question wasn't just who would play McGarrett—it was who played Danno on Hawaii Five-0 this time? The producers went in a radically different direction by casting Scott Caan.
Honestly, it was a stroke of genius.
Caan didn't try to imitate MacArthur. Instead, he leaned into the "fish out of water" trope. His Danny Williams was a New Jersey transplant who hated the heat, hated the ocean, and wore ties in the tropics just to spite the island lifestyle. This version of Danno wasn't just a loyal soldier; he was a partner who talked back. The "carguments" (arguments in the car) between Scott Caan and Alex O'Loughlin became the soul of the reboot.
Caan brought a frantic, neurotic, but deeply loving energy to the part. His motivation wasn't just "the job"—it was his daughter, Grace. This added a layer of vulnerability that the 1960s version rarely explored. Caan eventually earned a Golden Globe nomination for the role, proving that he had successfully stepped out of the long shadow cast by the original series.
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A Tale of Two Dannos: The Key Differences
If you sit down and watch an episode of the 1968 version followed by the 2010 version, the contrast is jarring. It’s almost like they are two different characters who just happen to share a name and a boss.
- The Vibe: MacArthur’s Danno was a professional. He followed orders and looked good in a suit. Caan’s Danno was a "Jersey Boy" through and through, constantly complaining about the lack of good pizza and the humidity.
- The Relationship: In the original, McGarrett was clearly the boss. In the reboot, it was a bromance. They were equals, even if McGarrett was technically in charge.
- The Family: We knew very little about MacArthur’s personal life on screen. Caan’s Danno was defined by his role as a father, often balancing high-speed chases with school plays.
There was also a brief moment in the 1997 failed pilot where the role was played by someone else entirely, but most fans prefer to pretend that didn't happen. It just didn't have the magic.
Why the Character Still Matters in Pop Culture
The reason we still care about who played Danno on Hawaii Five-0 is that the character represents the ultimate partner. Whether it’s the 70s or the 2010s, Danno is the person who has your back when things go sideways.
James MacArthur gave us the blueprint for the loyal TV detective. Scott Caan gave us the blueprint for the modern, emotionally complex partner. Both actors stayed with their respective shows for a decade or more, which is almost unheard of in modern television. MacArthur did 11 seasons; Caan did 10. That kind of longevity only happens when an actor truly inhabits a role and the audience refuses to let them go.
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Interestingly, both actors had famous fathers. MacArthur’s father was a titan of Broadway and film, while Scott Caan is the son of James Caan (of The Godfather fame). Maybe there’s something about growing up in the industry that gave both men the stamina to handle the grueling schedule of a procedural filmed on a remote island.
Actionable Insights for Fans and Collectors
If you're a fan of the franchise or a collector of TV memorabilia, there are a few ways to dive deeper into the history of these two actors and their time on the islands:
- Check the Credits: If you’re watching reruns and see a younger Danno, that’s James MacArthur. If he’s wearing a tie and looking annoyed, that’s Scott Caan.
- The "Lost" Pilot: Look for the 1967 pilot "Cocoon" if you want to see the "original" original Danno played by Tim O'Kelly. It’s a fascinating "what if" in TV history.
- The Final Episodes: To see how each actor’s journey ended, watch MacArthur’s final episode "The Skyline Killer" and Caan’s series finale "Aloha." They offer great bookends to two very different careers.
- The Catchphrase History: Note that while "Book 'em, Danno" was a staple of the original, the reboot used it sparingly as an homage, usually during pivotal season finales or significant emotional beats.
Knowing the history of these two men adds a layer of appreciation to the show. It’s not just a cop show; it’s a decades-long evolution of a character that has become a permanent part of the American lexicon. Whether you prefer the classic cool of the 60s or the Jersey grit of the 2010s, both actors earned their place in the Five-0 legacy.