Season 1: 2010 (Episodes 1- 20)
1. Fame - Ben's secret identity is exposed, casting him into the spotlight. Elsewhere, an alien plans to detonate a nuclear bomb.
2. Dubed - In order to be in more than one place, Ben uses Echo Echo to duplicate himself into three different Bens. Meanwhile, King Urien of the Forever Knights attempts to steal an ancient alien artifact.
3. Hit 'Em Where They Live - Zombozo, Charmcaster and Vulkanus form an alliance and plan to ambush Ben's parents.
4. Video Games - 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.
5. Escape From Aggregor - 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.
6. Too Hot To Handle - 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?
7. Andreas' Fruit - 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?
8. Fused - Ben is attacked by the 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.
9. Hero Time - Ben's childhood hero makes a comeback while he's on a date with a beautiful, young movie actress.
10. Ultimate Aggregor - Aggregor, having recaptured the five aliens, puts his ultimate plan into action.
11. Map Of Infinity - Ben must stop the newly transformed and extremely dangerous Aggregor from attaining the Map of Infinity.
12. Reflected Glory - 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.
13. Deep - 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.
14. Where The Magic Happens - Gwen is forced to team up with her nemesis Charmcaster when she finds herself in a hostile magical dimension.
15. Perplexahedron - 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.
16. The Forge Of Creation - When Aggregor goes after the limitless power of Alien X, Paradox steps in to stop him.
17. ...Nor Iron Bars In a Cage - Old feelings resurface when Kevin returns to the Null Void that housed him for years.
18. The Enemy Of My Enemy - When Argit and the Vreedle Brothers team up, they come up with a plan to attack the Plumber Academy.
19. Absolute Power: Part 1 - When Ben and Gwen are faced with an unexpected enemy, Gwen turns to Darkstar for help.
20. Absolute Power: Part 2 - Ben and Gwen are forced to go to Darkstar for help when they come across their most deadly, most unexpected foe yet.