WARNING: The following contains spoilers for One Piece Episode 967, "Devoting His Life! Roger's Adventure!" now streaming on Crunchyroll and Funimation.
Traveling One Piece's Grand Line is no easy feat, but thanks to some trailblazers, it's a lot easier than it used to be -- from the invention of the Log Pose to the Sea Train, characters on the sea have found new and ingenious ways to traverse it. But the Roger Pirates may as well have been laying down a trail of breadcrumbs in Episode 967, for the Straw Hats ended up following their path remarkably closely through the treacherous ocean waterways.
The episode opens shortly after the events of last time, alluding to the voyage's celebratory nature and the fact that it's a trip into the sea of memories for many fans with an old but familiar tune called "Bink's Brew." The song and all the emotions tied to it become the overarching musical backdrop for the episode as the crew visit many familiar places, including Skypiea, Water Seven and Fish-Man Island.
Just like Luffy and crew, the Roger Pirates arrive at Skypiea via the Knock Up Stream, though at a much more peaceful time during Ganfor's rule. Once there, they discover the Poneglyph and the golden bell. While Roger says they don't have enough time to take the bell, he does have Oden carve a message into the gold beside the Poneglyph -- the same message that Robin would find years later, leading her to believe that the Roger Pirates learned the entire history of the world.
Just like the Going Merry, Roger's ship, the Oro Jackson, was also damaged after falling from Skypiea. Thus the crew turned towards Water 7 -- and just like the Straw Hats, met Franky, though it's the young version who had just been abandoned by pirates, and is unwilling to join this particular set of ruffians. They chat briefly with Tom and Kokoro as well about Tom's yet-uncompleted Sea Train, further setting the stage for the Straw Hats' adventures with that very train.
They continue their journey all the way to the Sabaody Archipelago and Fish-Man Island. As Luffy would later, both Roger and Oden hear the voices of the Sea Kings eagerly awaiting the birth of their ruler as they travelled under the sea. Upon reaching Fish-Man Island, the newly crowned King Neptune gives them a rather uninviting welcome at the end of his spear. Here he reveals that Madame Shyarly has been making predictions that always come true (at the tender age of three no less) -- the current disaster they're trying to prevent is the destruction of the gate. While Roger insists that he and his crew mean no ill will, the Sea Kings break the gate, fulfilling the prophecy. Shyarly then explains that they're waiting for the birth of the mermaid princess, none other than Shirahoshi herself, who would eventually become Luffy's ally.
It is then revealed that one of the red Road Ponegylphs once resided at Fish-Man Island. Roger asks Neptune the identity of the weapon "Poseidon," with Neptune in turn explaining that once every few hundred years a mermaid is born with the ability to speak with the Sea Kings. While Roger correctly infers that this likely refers to Neptune's soon-to-be daughter, Neptune counters that just because it's called a weapon doesn't mean it has to be one -- a sentiment both Roger and Luffy seem to agree with.
So while the Oro Jackson's crew have their own goals in mind, the One Piece showrunners managed to squeeze in references and in-universe foreshadowing to the Straw Hats' journey through the Grand Line into twenty minutes -- while also showing viewers what the Roger Pirates actually got up to in these iconic locations.