Weekenders Adventures of The Lord of the Rings: The Return of the King is the third Weekenders/Lord of the Rings crossover made by Sonic876. It is sequel to Weekenders Adventures of The Lord of the Rings: The Two Towers.
Gandalf leads Aragorn, Legolas, Gimli, and King Théoden to Isengard where they reunite with Merry and Pippin, who helped the Ents destroy Saruman’s forces. With Saruman himself defeated, Gandalf retrieves Saruman’s palantír which is viewed by a curious Pippin, allowing Sauron to attack the Hobbit’s mind. Gandalf deduces Sauron will attack Gondor’s capital Minas Tirith, riding there with Pippin. They meet Lord Denethor, steward of Gondor, and Boromir’s father. Pippin declares his service to Denethor after Boromir died protecting him.
Meanwhile, Frodo Baggins and Samwise Gamgee are led by Gollum to Minas Morgul where they witness the fortress' lord, the Witch-king of Angmar leading an Orc army to drive Denethor’s youngest son Faramir and his men from Osgiliath. The three soon begin climbing an enormous stairway in the cliff face that would take them to Mordor. Having overheard Gollum's plot to regain the Ring, Sam keeps a suspicious eye on him. Following Gandalf’s instructions, Pippin secretly lights distress beacons to signal Théoden to assemble the Rohirrim for battle while Gandalf helps Faramir and men reach Minas Tirith.
While helping Théoden gather his forces, Aragorn is approached by Elrond who tells him that Arwen is dying after she returned to Riverdell upon seeing a vision of her son that convinced her to stay on Middle Earth. Elrond then gives Aragorn the sword Andúril, Isildur's sword Narsil reforged, so he can reclaim his birthright while gaining reinforcements from the Dead Men of Dunharrow. Joined by Legolas and Gimli, Aragorn travels to the Paths of the Dead, recruiting the Army of the Dead with the promise to release them from their curse once they fulfil their oath they made to Isildur.
Denethor falls into madness when he believes a wounded Faramir is dead from a futile effort to retake Osgiliath, leaving Gandalf to command the city defences against the Orc army under Gothmog. But as Gothmog's forces eventually force their way into the city, Denethor tries to kill himself and Faramir on a bonfire. Luckily, Pippin alerts Gandalf and they save Faramir while Denethor throws himself off the top of Minas Tirith as Théoden and the Rohirrim arrive. Initially having the advantage at the start of the Battle of the Pelennor Fields, the Rohirrim end up being overwhelmed by the Oliphaunt-riding Haradrim while the Witch-king mortally wounds Théoden. Though Théoden’s niece Éowyn, having posed as a male soldier, slays the Witch-King with Merry's help, Théoden dies of his wounds. Aragorn arrives with the Army of the Dead, quickly wiping out the Orcs and winning the battle. Once the battle ends, Aragorn allows the ghosts to pass on as Éowyn and the other wounded are tended to. Later, Aragorn and his friends agree to lead a united front to match towards the Black Gate as a distraction so Frodo and Sam get to Mount Doom.
Meanwhile, Gollum manipulates Frodo into leaving Sam behind before they arrive to the tunnel leading to Mordor. Gollum then leaves Frodo to get killed by the giant spider Shelob. Though Frodo evades Shelob, fighting Gollum off while revealing his intentions to destroy the Ring, the hobbit is paralyzed by Shelob. Though Sam returns and drives Shelob off, he takes Frodo's sword Sting and the Ring for safekeeping, believing him to be dead, before Frodo's body is taken by Orcs to Cirith Ungol. Realizing Frodo is alive, Sam gives chase and rescues Frodo, returning the Ring to him. With Aragorn's army holding off Sauron's forces, the Hobbits' are attacked by Gollum after they reach Mount Doom. Briefly evading Gollum, Frodo succumbs to the Ring's power, refusing to destroy it. However, Gollum attacks Frodo, biting his finger off to reclaim the Ring in a struggle that sends Gollum falling to his death with the Ring in hand. As Sam saves Frodo, the Ring and Sauron are both destroyed, causing an eruption that consumes Mordor and wipes out most of the fleeing Orcs. Gandalf flies in with eagles to rescue the Hobbits, who later reawaken in Rivendell and reunite with the surviving Fellowship members.
Aragorn is crowned King of Gondor and taking Arwen as his queen before all present at his coronation bowing before Frodo and the other Hobbits. The Hobbits return to the Shire where Sam marries Rosie Cotton. Frodo, unable to cope with the traumas of his journey, departs Middle Earth for the Grey Havens alongside his uncle Bilbo, Gandalf, and the Elves, leaving Sam the Red Book of Westmarch that details their adventures. Though saddened by Frodo's departure, Sam regains his joy when greeted home by his family.
- Ash Ketchum, Pikachu, Misty, Togepi, Brock, Sailor Moon and the Sailor Scouts, Sunset Shimmer, The Human Mane 5, Sci-Twi/Midnight Sparkle, Spike the Dog, Scooby-Doo, Shaggy Rogers, Fred Jones, Daphne Blake, and Velma Dinkley guest stars in this film.
- Kurumi Tokisaki, The Dazzlings, Principal Abacus Cinch, and Team Rocket will work for Sauron.