One Piece — Dreams!, The Zenny Pirate Crew Sortie!, Beyond the Rainbow
Season 5 of One Piece is mostly made up of original filler stories, meaning they are not part of the main manga storyline but focus on side adventures of the Straw Hat crew. The season begins with the “Dreams!” arc, where each Straw Hat reflects on their personal goals and motivations, highlighting their determination to continue their journey. Next is the “Zenny Pirates” arc, in which the crew encounters an elderly moneylender named Zenny who lives on an island with his unusual group of companions. What starts as a conflict gradually turns into mutual respect as the Straw Hats learn about his past. The final arc, “Rainbow Mist,” traps Luffy and his friends inside a mysterious, time-distorting fog. There they meet children who have been separated from their families for years due to the mist’s strange effects. The crew helps them uncover the truth behind the phenomenon and find a way back home.
Episodes

E131 The First Patient! The Untold Story of the Rumble Ball!
★ 7.1Nov 3, 2002 · 24m
After their adventures in Alabasta, the crew come upon another deserted island and split up tasks amongst themselves. Chopper is left in charge of guarding the ship, and he reminisces about the day he first made the rumble ball and his first patient, Dr. Kureha, while spending some time with the newest crewmember: Nico Robin.

E132 Uprising of the Navigator! For the Unyielding Dream!
★ 6.8Nov 10, 2002 · 24m
A weird salesman is fished out of the water and onto the Going Merry, and Nami buys a ton of "1000 year paper" from him to draw her sea maps. However, that's not going to be easy with the rest of the crew goofing off as usual.

E133 A Recipe Handed Down! Sanji, the Iron Man of Curry!
★ 6.9Nov 17, 2002 · 24m
The Going Merry runs into several Marine ships in some fog, and the Straw Hats meet a trainee Marine chef named Tajiyo. Sanji helps him out of a bit of cooking trouble.

E134 I Will Make it Bloom! Usopp, the Man, and the Eight-Foot Shell!
★ 6.9Nov 24, 2002 · 24m
The crew stops on an island that's having its annual fireworks festival; Usopp meets a young fireworks-maker named Kodama and helps her achieve her dream.

E135 The Fabled Pirate Hunter! Zoro, the Wandering Swordsman!
★ 6.6Dec 1, 2002 · 24m
Zoro has a flashback about the time when he first met Johnny and Yosaku, and faced off against Bandits and, Dick.

E136 Zenny of the Island of Goats and the Pirate Ship in the Mountains!
★ 6.7Dec 8, 2002 · 24m
After escaping from several Marine ships, the Straw Hats land on an uncharted island and meet an old man named Zenny. Chopper finds out that, because of his bad heart, Zenny probably only has three days to live.

E137 How's Tricks? The Designs of Zenny the Moneylender!
★ 6.9Dec 15, 2002 · 24m
The Straw Hats help Zenny out, hoping to make his last days good ones; they learn about Zenny's past as a money lender, and his dream of becoming a pirate. But Zoro realizes that Zenny has outlived Chopper's predictions and so the straw hats decide that, after helping him finish his pirate ship, they will leave the island.

E138 Whereabouts of the Island Treasure! Attack of the Zenny Pirates!
★ 6.8Dec 22, 2002 · 24m
Zenny decides to follow his dream and become a pirate, despite his age. He helps the Straw Hats out of trouble with the Marines, and then they part ways.

E139 Legend of the Rainbow Mist! Old Man Henzo of Luluka Island!
★ 6.4Jan 5, 2003 · 24m
On Ruluka Island, some of the Straw Hats make enemies of the Mayor and his men, who have placed high taxes on everything. Robin, Usopp, and Luffy meet Professor Henzo, who's doing research on the island's rainbow mist. When some of the mist shows up, Henzo borrows the Going Merry to go explore it.

E140 Residents of the Land of Eternity! The Pumpkin Pirates!
★ 6.1Jan 12, 2003 · 24m
The inside of the Rainbow Mist full of wrecked ships and treasure, and is guarded by five kids. The kids are actually friends of Henzo's that got lost in the mist over 50 years ago.

E141 Thoughts of Home! The Pirate Graveyard of No Escape!
★ 6.4Jan 19, 2003 · 24m
Henzo, his friends, and the others try to find a way out of the ship graveyard. Meanwhile, the Mayor and his men let the information about the Rainbow Mist slip to the remaining Straw Hats still on Ruluka.

E142 An Inevitable Melee! Wetton's Schemes and the Rainbow Tower!
★ 6.2Jan 26, 2003 · 24m
Luffy accidentally propels himself and Rapanui to the end of the mist. Nami appears in the ship graveyard with a rowboat full of treasure and a string connected to the real world, which are both stolen by Wetton's subordinate. The Mayor uses the Rainbow Tower to make a bridge to the Rainbow Mist.

E143 And so, the Legend Begins! To the Other Side of the Rainbow!
★ 6.2Feb 2, 2003 · 24m
The Going Merry escapes from the Rainbow Mist, getting badly damaged on the way. The Mayor gets arrested by a bunch of powerful marines that turn out to be older versions of Henzo's friends, who were thrown 50 years into the past by the Rainbow Mist's collapse.
Other Seasons
EPS61East Blue1999
EPS16Whiskey Peak & Little Garden
EPS14Drum Island
EPS39Alabasta
EPS52Skypiea
EPS33G-8 & Long Ring Long Land
EPS35Water Seven
EPS73Enies Lobby
EPS45Thriller Bark
EPS26Sabaody Archipelago
EPS14Amazon Lily
EPS101Impel Down & Marineford
EPS58Fishman Island
EPS62Punk Hazard
EPS50Dressrosa
EPS56Dressrosa (2)
EPS55Zou2016
EPS74Whole Cake Island2017
EPS14Levely Arc2019
EPS197Wano Country Arc2019
EPS67Egghead
EPS26Elbaph