One Piece is a juggernaut of a series. Clocking in at over 1000 episodes, One Piece has more episodes than other anime have fans. Normally, series that run for as many episodes as One Piece usually shun long-term storytelling in favor of episodic adventures.
Other anime, like Pokémon and Crayon Shin-Chan, lean towards developing episodes with an overarching plot that binds all of the series' events. One Piece is unique in that it's intensely focused on conveying one specific story. As a result, several episodes are too crucial for fans to miss.
10 Episode 194: The First Appearance Of The Gold Poneglyph
Poneglyphs are the most important items next to the mysterious One Piece in the series. Most of the pivotal episodes in One Piece center around either the reveal of a poneglyph or the information contained on one.
Although fans already saw a Poneglyph in Alabasta, it was Robin's discovery of the gold poneglyph that gave the first major clues to the location of the One Piece. Initially unimpressed by the information on the glyph, Robin later finds Gol D. Roger's name inscribed on the relic.
9 Episode 277: Ohara Burns To The Ground During A Buster Call
Robin is arguably one of the most essential member of the Straw hat pirates. Without her knowledge of the poneglyphs, Luffy would have no route to Laughtale and the One Piece. In episode 277, fans learn exactly why Nico Robin is so valuable: her island of Ohara was obliterated by the World Government.
Before the massacre, Robin's mentor Professor Clover shares vital information about the infamous void century. As he gets ready to share a damning secret about the World Government, he is brutally murdered.
8 Episode 314: Fans Learn About Luffy's Paternal Lineage
One Piece characters are usually renowned for their tragic and complex backstories. Before a Straw hat becomes Nakama, fans receive a touching, heart-wrenching origin that explains their motivation and personality. It's strange to realize that Luffy didn't have a concrete backstory until after the Marineford war.
Episode 314, however, laid the groundwork for Luffy's eventual origin story. The episode introduces fans to Monkey D. Garp, who shares details about the New World with Luffy. Garp also name drops Luffy's father, the revolutionary Monkey D. Dragon.
7 Episode 400: Roger And Rayleigh Share The Secrets Of The World
It's always fun to remember an old friend. When facing the twilight of one's life, memories of the good times are the only thing that remains.
In Rayleigh's case, those memories are always going to center on the enigmatic Gol D. Roger: the pirate king. In episode 400, Rayleigh provides the Straw hat crew and fans with a vital information dump that fills in some very vacant gaps in the understanding of the One Piece. The episode ends when a remorseful Rayleigh fondly remembers Roger.
6 Episode 516: Rayleigh Finally Explains Haki
Most shonen anime have their own fictional power system. One Piece happens to have two power systems that counter each other. For several episodes, fans saw glimpses of haki and how powerful it could be but got very little information about the power system.
In episode 516, Rayleigh takes Luffy to a secluded island to train for two years. Before he can begin his tutelage, Rayleigh breaks down the complete haki system in full detail. By the end, both Luffy and the fans are knowledgeable.
5 Episode 649: Fans Learn About Poseidon
One Piece's cast overflows with characters. Oda populates every arc with more characters than the previous one. In other shows, fans would label the characters as superfluous, but that's a foolish idea in One Piece, as any character could become massively important.
In episode 649, fans discover that the whiny princess that Luffy protected in the last 30 episodes is one of the ancient weapons. Fans were aware of ancient weapons, but episode 649 was the first time they learned a character could be one.
4 Episode 769: Fans Learn About The Final Clues To The One Piece
One Piece is coming to an end. Not in the next few months, but the writing is on the wall for the series' final arc. In episode 769, fans learn about the red poneglyphs. When the giant relics are deciphered and assembled, they lead directly to Laughtale and the One Piece.
The inclusions of the red poneglyphs are a bittersweet moment for fans of the series as they guarantee an exciting journey and a looming climax to the beloved series. One Piece is almost over.
3 Episode 889: Fans Meet Imu Sama For The First Time
Most fans believed they had an accurate perception of how power got distributed in the One Piece world. Outside of the Fleet admiral, fans believed that the Gorosei pulled the strings in the series. In episode 889, after the Reverie, fans discovered that even the Gorosei bows to a sovereign.
The concept is still such a massive shock, and every fan is grappling with the reveal in their own way. Will the mysterious Imu Sama be the final boss for the endgame of the series?
2 Episode 958: The One Piece World Gets Rocked
Similar to the reveal of Imu Sama, fans were blown away to discover that Roger had a rival that arguably surpassed him. While Roger went on to become the most celebrated legend of the seas, Rocks D. Xebec got erased from history.
In episode 958, former Fleet admiral Sengoku holds a special meeting within the navy to reveal a concealed history of global affairs. Fans learn that Garp and Roger teamed up to battle the impossibly powerful Rocks pirates. Rocks' crew even included three emperors.
1 Episode 968: Roger Becomes The King Of The Pirates
It takes a lot of dedication to reach episode 968. Many anime fans avoid watching One Piece based on the length of the series alone. However, once fans reach the episode, One Piece pays off their investment tenfold.
In episode 968, fans watch the final adventures of Gol D. Roger as he finds the fabled One Piece. Prior to this point, fans believed Roger had left the treasure, but it turns out that he was "too early" to use the booty he discovered at Laughtale.