Ben 10: Aliens Unleashed is the fan-created fourth incarnation of Cartoon Network's Ben 10 franchise created by "Man of Action" (a group consisting of Duncan Rouleau, Joe Casey, Joe Kelly, and Steven T. Seagle).
Present-day Ben's new Omnitrix malfunctions, causing trouble for both Ben's 10-year-old self and Ben 10,000, who are busy saving the world in their own time periods. All three versions of the hero are haunted by nightmares of the Diagon after present-day Ben, who has been traveling the world with Kevin and Gwen, learns that Azmuth has mysteriously disappeared, and whenever the Bens transform, they find themselves attacking those they care most about as if being controlled by someone else. Things only get worse when the Omnitrix aliens materialize in the real world and attack, trapping the Bens, who have lost their ability to transform, inside their watches.
Young Ben, present-day Ben, and Ben 10,000 awaken in the city-like dimension within the Omnitrix, able to transform once again simply by wishing it, for the Omnitrix is no longer on their wrists. The three, whose watches are connected across time and space, team up and travel through the Omnitrix in an effort to escape.
Back in the real world, tensions rise between Kevin and Gwen. Feeling used and betrayed by Ben, Kevin ends his relationship with Gwen and begins a new life of low-key crime and Plumber work. Gwen learns from Grandpa Max that with Ben gone and possibly dead, she is the last hope to the universe. However, Gwen still senses Ben's manna and, desperate to find and rescue him, travels to Anodyne to become a full Anodyte with help from Grandma Verdona.
Before it is too late, Professor Paradox forces Kevin and Gwen to reunite; to end the coming crisis, they must fight as a team. Paradox confirms that Ben is still alive, but he also goes on to state that Ben is in the middle of the most difficult battle of his life against an adversary stronger than any he has ever faced before: himself. Paradox reveals that because Ascalon and the Omnitrix share the same core energies, when Ben used the sword to defeat Vilgax and rob him of the Diagon's power, the demon's consciousness entered Ben's body and fused with his DNA. Paradox states that the Diagon has taken over the Omnitrix, and he's using the aliens within it in a second effort to conquer the universe.
Kevin and Gwen agree to team up once again in an effort to free Ben from the Omnitrix. Unable to simply destroy the watch because doing so would also destroy Ben and his transformations, they use the Rustbucket to travel cross-time with help from Paradox, hoping one of the parallel dimensions will lead them to the world contained within the Omnitrix. Kevin and Gwen's journey takes them to many of Ben's Omnitrix aliens' home planets, on which they fight evil versions of the aliens themselves.
Inside the watch, young Ben, present-day Ben, and Ben 10,000 find Azmuth under attack from some of the Omnitrix aliens. The heroes rescue the Galvan, who, despite how tired and weak he is, reveals he had neutralized his DNA on Primus to enter the Omnitrix after detecting a dangerous space-time anomaly in hopes of resolving it. After admitting his failure to do so, Azmuth explains that the Omnitrix is what holds the universe together, for the watch contains its DNA. Now that the Diagon has taken the watch and Ben's transformations over, he intends to use Ben's strongest form, Alien X, to tear the universe apart and rebuild reality itself. The Omnitrix is the universe's last hope, and Azmuth reveals that the only way the Diagon-controlled Alien X can enter the real world like Ben's other Diagon-controlled transformations is if Ben is able to escape from the watch. Realizing how critical Azmuth's condition is, present-day Ben resolves to get the elderly Galvan out of the watch before it is too late for him, no matter what the consequences are.
Kevin and Gwen's journey across time and space yields an army of alternate versions of Ben who are willing to fight alongside them to save their universe. They even reluctantly recruit Albedo, the only other Galvan besides Azmuth who knows enough about the Omnitrix to fix or destroy it, depending on the situation.
Pursued by the Diagon-controlled aliens, young Ben, present-day Ben, and Ben 10,000 finally manage to get Azmuth to the exit portal that would allow them to escape the Omnitrix. However, before they can escape, the Diagon-controlled Alien X reveals itself to the heroes, along with another army of Ben's evil transformations. A battle ensues to prevent the Diagon from entering the real world, but Azmuth sacrifices himself and chooses to hold the evil aliens off while the Bens escape before it is too late. Before returning to the real world, Azmuth tells present-day Ben to recall that the aliens are not his power; his power is the aliens. Ben screams in defiance as the aliens close in on the Galvan, but before he can come to Azmuth's aid, he finds himself in the real world.
Young Ben, present-day Ben, and Ben 10,000 are horrified to see the Omnitrix world and real world fusing together. They can still transform simply by wishing it due to the absence of the Omnitrix from their wrists, but they find that every living thing on Earth is being transformed into Ben's aliens. The Bens realize much to their chagrin that Azmuth died in vain; because the real world and the world within the Omnitrix are now one and the same, the Diagon-controlled Alien X and its reinforcements can enter the real world at will.
The Bens reunite with Kevin and Gwen just in time for the Diagon-controlled Alien X to arrive with an army of aliens. The alternate Bens, Kevin, and Gwen face off against these while present-day Ben goes after Alien X. As reality falls apart around them, Ben learns the hard way just how powerful Diagon's power has made Alien X. The evil Celestialsapien absorbs all of its alien accomplices into its body, and using their combined powers, destroys every alternate version of Ben except for the true young Ben and Ben 10,000. Kevin, Gwen, and Albedo are also incapacitated. Ben and Alien X are the last two standing.
Alien X continues to taunt Ben, stating that it is too late to save the universe, and even if Ben destroys him, he'll be destroying himself, as well. Ben reveals he doesn't care, and after Alien X claims he's not nearly powerful enough to even scratch him, Ben understands the true meaning behind Azmuth's last words. All this time, he has been the one saving the world, not the aliens he transforms into. The aliens will always be a part of him, Omnitrix or no Omnitrix. This lets him take on the form of Ultimate Ben, which he uses to destroy Alien X.
Reality pieces itself back together as Kevin, Gwen, Albedo, young Ben, and Ben 10,000 regain consciousness. The Omnitrix returns to Ben's wrist. Azmuth is revived now that things are back to the way they were before his death, and he restores Albedo's Galvan form and makes him his apprentice once again as a reward for his recent heroics. Professor Paradox takes young Ben and Ben 10,000 back to their own times, but not before he tells present-day Ben to enjoy his brief respite because things will only get harder for him as time goes on. Before the hero can comprehend Paradox's words, Ben, Kevin, and Gwen find themselves back in their own time with no memory of past events; they assume they all had the same weird dream and depart for a new Plumber mission.
Armed with the powerful new Alien Assault Vehicles, as well as some new transformations, Ben travels to the Andromeda galaxy with Kevin and Gwen to face a new threat.
- Main article: List of Ben 10: Aliens Unleashed Episodes
Ben 10: Aliens Unleashed features 50 episodes, which span over two seasons.
The true Omnitrix
- Main article: List of Ben 10: Aliens Unleashed Aliens
Principal voice actors
- Yuri Lowenthal - Ben Tennyson, Albedo, Alien X
- Ashley Johnson - Gwen Tennyson
- Greg Cipes - Kevin Levin
- Dee Bradley Baker - Humungousaur, Jetray, Chromastone, Spidermonkey, Echo Echo, Big Chill, Upchuck, Cannonbolt, Lodestar, Swampfire, Armodrillo, Goop, Nanomech, Way Big, Brainstorm, Water Hazard, Terraspin, AmpFibian, Heatblast, NRG, Diamondhead, Wildmutt, Eatle, Fasttrack, ChamAlien, Clockwork, Jury Rigg, Four Arms, Stinkfly
- John DiMaggio - Rath, Diagon
- Paul Eiding - Max Tennyson
- Vyvan Pham - Julie Yamamoto
- Tara Strong - Young Ben Tennyson, Serena (Alien X)
- Sean Donnellan - Ben 10,000
- Jeff Bennett - Azmuth, Bellicus (Alien X), Ghostfreak
- David McCallum - Professor Paradox
- Juliet Landau - Verdona Tennyson
- Main article: Ben 10 Aliens Unleashed: Andromeda Attack
Like Ben 10, Ben 10: Alien Force, and Ben 10: Ultimate Alien before it, Ben 10: Aliens Unleashed received at least one video game adaptation; the first was Ben 10 Aliens Unleashed: Andromeda Attack. Featuring more playable characters and aliens than ever before, the game takes place in the Andromeda galaxy in a timeline parallel to that of Ben 10: Aliens Unleashed. The game focuses on the utilization of Ben's new alien forms, as well as the powerful Alien Assault Vehicles.
- Main article: Punch Time Explosion: Ben 10 Takeover
A second Ben 10-related video game was released in connection to Ben 10: Aliens Unleashed: Punch Time Explosion: Ben 10 Takeover. A spin-off of Cartoon Network: Punch Time Explosion, the game features a cast of playable characters from Ben 10, Ben 10: Alien Force, Ben 10: Ultimate Alien, and Ben 10: Aliens Unleashed. These characters range from several of the protagonists from the Ben 10 franchise, to various antagonists, to all of Ben's alien forms.
- It was revealed by series-creator Omega Omnitrix that the series' title was chosen to reference two things: First, over the course of the series, Ben "unleashes" his true potential as a hero and wielder of the Omnitrix. Second, in the series' first season, the main antagonists are Ben's aliens themselves, who are "unleashed" from the Omnitrix and proceed to wreak havoc across the universe.