The following is a list of episodes for Ben 10: Ultimate Alien. A total of fifty-two episodes have been ordered. Episodes 1 through 10 were intended be season 1 and episodes 11 through 20 were to be season 2 but it was merged into one season due to Cartoon Network's schedule.
Dwayne said in his blog that the seventh episode of the second season would introduce the second season story arc, but once again due to Cartoon Network airing issues the story arc was split into two seasons.
In order to be in more than one place, Ben uses Echo Echo to duplicate himself into three different Bens (logical, sensitive and arogant). Meanwhile, King Urian of the Forever Knights attempts to steal an ancient alien artifact.
After defeating Ssserpent by using Four Arms for the first time in 6 years, Ben's celebrity status lands him a starring role in a video game and is asked to show all of his aliens' abilities. In reality, TV reporter Will Harangue has been using the video game as an excuse to build a giant spider-like robot that knows all of Ben's alien forms' moves and use them against him.
After defeating Dr. Animo, Ben, Gwen and Kevin encounter Galapagus, one of the aliens captured by the villain Aggregor and learn the story of how the aliens escaped and what Aggregor wants them for.
P'andor, the third alien on the run from Aggregor, seeks a means to escape from his containment suit. When Kevin discovers P'andor's secret, can he convince Ben and Gwen that he might not be as innocent as Aggregor's other prisoners?
Ben, Gwen and Kevin discover that Argit has become the leader of the Forever Knights with the help of Andreas, the fourth of Aggregor's former prisoners. However, when the Forever Knights rebel against Argit, can the trio save Andreas from a medieval execution?
Ben is attacked by Ra'ad, the last of the Andromeda Five, who blames him for Aggregor recapturing the others. During the battle, Ra'ad attempts to destroy the Ultimatrix and ends up merging with Ben. To make matters worse, Ben and the others finally come face to face with Aggregor who has no intention of leaving until he regains the final alien of his collection.
Cash and J.T. boast that they were the masterminds behind Ben's exploits and land themselves a TV series called "Alienated." After the promise of a paycheck, Ben and the gang decide to let Cash and J.T. tag along on their adventures. Unfortunately, Vilgax's old partner Psyphon believes that Cash and J.T. are the actual brains behind the operation and plans to destroy them.
In order to stop Aggregor from obtaining another piece of the Map of Infinity, Ben and the gang travel to the depths of a planet covered entirely in water.
With the fourth piece of the Map of Infinity almost in Aggregor's clutches, the gang chase him through the artificial planetoid known as Perplexahedron.
A ship crashes down onto Earth, and inside the ship is a mysterious alien girl named Eunice. Eunice has no recollection of what happened before her crash landing, and to add to the chaos, Eunice is being hunted by Sunder.
Gwen is excited by the prospect of her cousin paying the team a visit, but her excitement quickly turns into trepidation when it is uncovered that her cousin is not all that she appears and has some particularly sinister intentions.
Gwen has always been a multi-tasker, trying to juggle school, hobbies, friends and her work as a hero, waking up early and going to sleep late. But Gwen's already packed day is about to get worse when Dr. Animo attacks with an army of giant frogs and Gwen is forced to make a hard choice.
Eon has returned to plague not just Ben but every version of Ben across space and time. To stop him, Ben teams up with his future counterpart, Ben 10,000 and Professor Paradox in order to destroy the Hand of Armageddon.
When Grandpa Max receives a distressing call from Area 51, the team dispatches to investigate. Upon arrival, Ben and the gang learn that the facility was secretly being used as a housing unit for potentially dangerous aliens. As Ben searches the facility, he discovers that a prisoner has escaped the compound and stolen a Plumber spacecraft. Now Ben is forced to chase down the escaped alien and determine whether or not the alien is as dangerous as Colonel Rozum believes it to be.
Ben finds himself in a potentially seriously dangerous situation when he discovers that Vulkanus has put out a hit on him and sent out an army of deadly Techadon robots who are dead set on making sure Ben meets an untimely demise.
Ben and the gang head out on an exciting ocean adventure when they decide to try to determine the cause of a strange phenomenon and travel far out into the Pacific Ocean to thoroughly investigate the Pacific Garbage Vortex.
After arriving in Rex's world, Ben Tennyson has no other choice than to team up with Providence's secret weapon - Rex Salazar - in order to defeat a new, very dangerous threat.
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