So, by combining the plot summary of The Empire Strikes Back from Wikipedia with characters from the Avengers and other Marvel properties, I have created Ultron Strikes Back, a fictional movie set on a post-apocalyptic Earth ravaged by Ultron; please note that due to the nature of the original plot, some characters and objects have been changed drastically in order to fit in, so bear with me while I go over them:
- James Rogers: The son of Captain America, who was given his father's shield by Hank Pym; stand-in for Luke Skywalker
- Clint Barton: Smuggler/marksman nicknamed "Hawkeye"; stand-in for Han Solo
- Natasha Romanoff: SHIELD leader with a mysterious past; stand-in for Princess Leia
- T'Challa: Ruler of Wakanda who betrays the heroes to protect his nation from Ultron; stand-in for Lando Calrissian
- Jarvis: An AI program based on the late Edwin Jarvis; stand-in for C-3PO
- The Vision: A former Avenger reprogrammed with the brain patterns of Captain America and loyalty to Ultron; stand-in for Darth Vader
- The Hulk: Gamma-powered brute and partners with Clint Barton; stand-in for Chewbacca
- Beast: Former Avenger and mutant friends with the deceased Wonder Man, the original template for the Vision; stand-in for Yoda
- Bullseye: The Kingpin's favorite assassin; stand-in for Boba Fett
- Ultron: Genocidal robot with an army of clones to wipe out all humans; stand-in for the Emperor
- Hank Pym: Former Avenger, creator of the Vision, and James' mentor until his death; stand-in for Obi-Wan Kenobi
- Asteroid M: Orbital asteroid base created by Magneto, then taken over by Ultron and used as a weapon
- Iron Man armor: One of the only remaining armors created by Tony Stark, stuck in autopilot mode; stand-in for R2-D2
- Ultimo robots: Giant indestructible robots copied from alien technology by Ultron
And with that out of the way, here's the plot summary for Ultron Strikes Back:
"Three years after the destruction of Asteroid M, SHIELD has been driven from their former base in New York City by Ultron. SHIELD, led by Natasha Romanoff, have set up a new base in Jotunheim. Ultron’s army, led by the Vision, continues to hunt for SHIELD's new base by dispatching probe droids across the planet. James Rogers is captured by a frost giant while investigating one such probe, but he manages to escape from the frost giant's cave with his shield. Before James succumbs to the freezing temperatures, the spirit of his late mentor, Hank Pym, instructs him to go to the ruins of the X-Mansion to train under the Beast. James is found by Clint Barton, and the duo are eventually rescued by a search party.
Meanwhile, the probe alerts Ultron to SHIELD's location. Ultron launches a large-scale attack, using Ultimo robots to capture the base, which forces SHIELD to retreat. Clint and Natasha escape on the Quinjet with Jarvis and Hulk, but the ship's rocket boosters malfunction. They hide in a forest, where Clint and Natasha grow closer and eventually kiss. Vision summons bounty hunters to assist in finding the Quinjet. James, meanwhile, escapes with the Iron Man armor in his jet and crash-lands in front of the X-Mansion. He meets an ape-like creature who reveals himself to be Beast; after conferring with Hank's spirit, Beast reluctantly accepts James as his student.
After evading Ultron’s army, Clint's group travel to the hidden nation Wakanda on the continent of Africa, which is run by Clint's old friend, T’Challa. Unbeknownst to the group, the bounty hunter Bullseye tracks the Quinjet; shortly after their arrival, T’Challa leads the group into a trap and they are handed over to the Vision and Bullseye. Vision plans to use the group as bait to lure out James, intending to capture him alive and take him to Ultron. James sees a premonition of Clint and Natasha in pain and, against the wishes of Beast and Hank, abandons his training to rescue them.
Vision intends to hold James in suspended animation via carbon freezing, and selects Clint to be frozen as a test subject. Clint survives the process and is given to Bullseye, who intends to deliver Clint to the Kingpin. T’Challa initiates an escape and frees Natasha and the others, but they are too late to stop Bullseye from departing with Clint. They fight their way back to the Quinjet and flee Wakanda. Meanwhile, James arrives in Wakanda and engages with Vision in a duel that leads them over the nation's central mineshaft. Vision shatters James's shield, disarming him; when James refuses to join Vision against Ultron, accusing him of murdering his father, Vision reveals that he, in fact, has his father’s brain patterns. Horrified by the truth, James intentionally falls into the mineshaft and is ejected outside the African nation, where he grabs onto an antenna. He makes a plea to Natasha, who hears it and persuades T’Challa to return for him in the Quinjet. After James is brought on board, they are chased by Ultron robots but the Iron Man armor reactivates the Quinjet's rocket boosters, allowing them to escape.
Aboard a research frigate in the SHIELD fleet, James's shield is replaced with a hard-light shield. T’Challa and Hulk set off for Hell’s Kitchen in the Quinjet in order to find the Kingpin and save Clint. As the Quinjet departs, James, Natasha, the Iron Man armor, and Jarvis gaze out on the planet and await word from T’Challa."