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This article is about the crossover. You might have been looking for Heroes United (Online Game).

Ben 10/Generator Rex: Heroes United is a crossover episode animated in Generator Rex's art style with an appearance by Ben Tennyson. It was produced and aired as an episode of Generator Rex.


The story begins with a mysterious rift opening in the skies above New York City, attracting the attention of Providence. Meanwhile, Rex is sparring against Agent Six, while musing about his need for a "Theme song" (and briefly performing a take on the original Ben 10 theme song) before getting the alert about the rift. Providence, at the same time, is unable to do anything before Rex arrives with Six and Bobo. Rex attempts to touch the rift to see if it has something to do with nanites when Holiday then gets a scan that shows something is coming through the rift, and Rex finds himself face to face with Humungousaur, who knocks Rex back into the park beneath them. During their skirmish, a strange metallic creature also appears and heads into the city, with Bobo and Six on its trail while Rex continues to battle Humungousaur. Just when Rex thinks he has the upper hand on the monster, Humugousaur transforms in a flash of light into Diamondhead. Rex attempts to cure Diamondhead but to no avail, which surprises Rex.

Meanwhile, Six engages the creature and manages to cut a piece of it off, and when Holiday's scans give insufficient data, is given to Rex's older brother, Caesar. Both hero's battle then winds up on the Brooklyn Bridge after Rex lands a well-placed punch. Diamondhead gets up and transforms into Lodestar, attempting to counter his opponent's metal-based abilities. However, Rex quickly adapts and blasts Lodestar with his Slam Cannon into a Billboard. It breaks free of its binding, which forces the two to stop fighting, with Lodestar transforms into Rath to save the news reporter, Diane Farrah while Rex saves the other civilians. During Rath's discussion with Dianne, Rex then does a surprise drop on Rath and once again attempts to cure him, only for it not to work again. After attempting to explain himself, Rath decides to transform back into his true form, Ben Tennyson. Ben is shocked to learn that no one knows about him. Just then, Six appears with the mechanical creature from before, which self-destructs and renders him comatose and Rex mortified and angered.

Diamondhead fighting Alpha

In Providence HG's infirmary, Holiday explains that the creature was Nanite in origin, but somehow completely different from any EVO they have ever encountered. White Knight points out that part of it got away and that they were now searching for it. Ben says that they are probably dealing with a parallel universe issue. Holiday doubts his assumption, stating that parallel universes are just a theory to which, Ben replies that he has traveled to many of them. Ben says that they need to go out and search for it. Rex remarks that there is no way Ben can escape, but Ben manages to transform into Big Chill and flies off with Rex in hot pursuit. Big Chill visits the area where Bellwood should be and transforms back into Ben, and finding that himself, Gwen, Max, and Kevin do not exist in this world, nor does Mr. Smoothy (instead it is "Bob's Biscuit Barn"), Ben finally comes to grasp that he must be in an alternate dimension and both finally come to a truce. Caesar then appears and seemingly prepares to attack the two with a ray gun, which was actually intended for the energy ball, which is revealed to be the Alpha Nanite, the first nanite and a creation of Caesar's. The Alpha Nanite then begs Caesar to help him stabilize a new body to which Caesar refuses. Ben as Diamondhead knocks Alpha away from Caesar and manages to force Alpha to leave.

After escaping the creature, Caesar explains that he created Alpha as a means of controlling the nanites during the Nanite project, but it's the nanite form which is unsustainable and every body it builds burns out in short amount of time. When Alpha attempted to take organic bodies, this forced Caesar to banish it to another empty dimension.

Ben surmises it must have been the Null Void where it wound up, and that Alpha must have possessed alien life to sustain itself. Caesar explains that the damaged ray gun was to stop Alpha, who then attacks and destroys his research pod. Caesar escapes via the escape pod, leaving behind the two heroes. Ben transforms into Cannonbolt and saves Rex, to which the latter complains of the smell. Alpha then attacks Providence in order to absorb the E.V.Os inside for their nanites. When Ben and Rex arrive, they fight the Alpha where it attempts to absorb Rex's Omega-1 Nanite but fails. Ben and Rex eventually manage to drive Alpha off, and then slowly bond after sharing their origins during a small game of hoops.

Rex and Ben accidentally wear each other's jackets

White Knight then reveals that Alpha has gone to the Bug Jar, which is the largest concentration of active nanites on the planet after the Nanite Event. White Knight and the heroes arrive, only to find they are too late to stop Alpha from absorbing the nanites of all the EVOs that were in the Bug Jar to become a colossal monster that begins to attack the three of them. Alpha is unable to absorb Rex's Omega-1 Nanite so he decides to hack Ben's Ultimatrix which gives him access to his own nanite corrupted version of it and 3 of Ben's strongest aliens, Heatblast, Four Arms, and Humungousaur. During the battle, Ben transforms into a new alien named Shocksquatch, which only lasts a few seconds but enough to stop Alpha momentarily. Using an odd form of teamwork, Rex is able to disable Alpha's imitation Ultimatrix powers, but is ensnared by his enemy and robbed of his Omega-1 Nanite, leading to Nanite Alpha to transform into a colossal crab-centaur-like being calling itself Alpha-Omega; the beginning and the end.

Upgrade merged with Rex

As the now nearly unstoppable Alpha-Omega rampages through the Bug Jar; synthesizing the ruined structures in order to create new nanites for itself, Rex has doubts about himself now that his most powerful builds are gone. Ben, however, comes up with a plan, and transforms into Upgrade and merges with Rex, Thus providing him with the Upgraded versions of his Original 6 builds. After a couple seconds, the duo then take on the Alpha-Omega, to which they hold their own for a short while. At the last minute, Rex comes with a plan and both do a final bout of teamwork. Rex locates the Omega-1 Nanite inside of Alpha Omega and shoots Ben as canonbolt directly at the monster, using his Slam Canon, which forces the monstrosity into a large cloud-like entity. Rex then uses his abilities to begin to dense the nanite cloud into a small sphere. While this happened, Caesar appears and extracts the Omega-1 Nanite. Attempting to dispose of Alpha, Caesar then opens a rift for Ben, who transforms into Murk Upchuck and swallows the compacted Alpha as he departs to the Null Void and back to his own Earth, but not before weirding out Rex one last time.

In the epilogue, Rex is overjoyed that Six has recovered, and wonders if he'll ever see Ben again. Six suggests that they possibly will if fate had ordained for them to meet once already. Caesar appears and injects the Omega-1 Nanite into Rex. Rex doubts that Caesar could have accidentally brought the alpha Nanite, although Caesar assures him that there is a 99.998% chance that it is Omega-1.

In the final moments, in the depths of the Null Void, Alpha begins to stir within its prison of matter, causing it to glow and crack apart.

Noteworthy Events

Major Events

Ultimatrix Alien Debuts


Flashback Characters


Aliens Used

By Ben

Flashback Only Aliens

By Alpha



Rex: (singing to the theme of the Ben 10 theme song) It started when the nanites went ka-pow upon the scene. Transforming all the lifeforms like nothing you've ever seen. But there's one lucky hombre that can make them build machines: He's Gen Rex.

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Humungousaur: You and your partners are gonna call it quits right now, and I'll keep the pounderizing to a minimum.
Rex: I was gonna say the same thing, only in Spanish.

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Reporter: Thank you, Wh-- Who are you?
Rath: Seriously? I'm the cat who's all that! The Rath Attack! Eh, but I have heard of other things.

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Ben: There's no Mr. Smoothy here. That's messed up.
Rex: My partner is in a coma. If your stressing over a frozen drink, YOU ARE TOTALLY GETTING PUNK-BUSTED!!!

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Rex: Feel like giving me a hand?
Ben: How about four? (Transforms into Four Arms)
Rex: I'm starting to like the way you think, Ben 10.

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Ben: It started when the Omnitrix fell out of the sky; I was ten years old.
Rex: Six years ago, the Nanite Event changed everything!
Ben: And there's alien DNA in the Omnitrix!
Rex: And that's how I could build stuff with the micro machines in my body!
Ben: Now Kevin, Gwen, and I are the Plumbers!
Rex: Plumbers? And I thought Providence was a dumb name!
Both: HA HA HA!

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Ben: If this is the Bug Jar - where are the bugs? (Large swirl of gray wind appears)
Diamondhead: Whoa, what do you call that?
White Knight: I call the entire nanite population of the Bug Jar.

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White Knight: Don't let it get to Rex- if it drains his nanites... (talking about Alpha)
Diamondhead: Game over. Understood!
Rex: It already tried to eat me - that didn't work.
White Knight: That thing was made to control machines.

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Rex: I could use an alien right now! (gets absorbed by Alpha Nanite)
Ben: Great idea! But a certain nanite monster busted my watch!

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Rex: Do something - ANYTHING! (being absorbed by Alpha Nanite)
Ben: (Tries to throw a tiny rock at Alpha, but misses, and hits Rex)
Rex: Do something BETTER!
Ben: I could try calling it names!
Ben: (to Alpha Humungousaur) Hey jerkasaur! You're a loser!

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Rex: My most powerful builds came from the Omega nanite. A lot of people are going to get hurt and I can't stop it. What happens when the best you can do just isn't enough.
Ben: You get an upgrade!
Rex: Weren't you listening? Alpha has the Omega.
Ben I'm not talking about a Nanite here. (transforms into Upgrade)
Rex: Hey, what are you... (Upgrade goes inside Rex's body) Whoa, okay, that feels weird. (Upgrade changes his body into a suit) Whoa. What suppose to happen now? (Upgrade's head appears on Rex's left arm, making Rex shocked) Uaa.. don't do that, you freaking me out.
Upgrade: Build something!
Rex: (Makes a Smack Hand on his right arm and it grows spikes) Sweeeet, so what's the plan?
Upgrade: You build stuff, I make it better. Fight fight fight. We win!
Rex: Works for me! (Rex make a Boogie Pack and goes flying) Woohoo!

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Naming and Translations

Language Name Origin
Italian Ben 10/Generator Rex: Heroes United Ben 10/Generator Rex: Heroes United
Polish Ben 10-Generator Rex: Przymierze Bohaterów Ben 10-Generator Rex: Hero Alliance
Portuguese (Br) Ben 10/Mutante Rex: Heróis Unidos Ben 10 / Mutant Rex: United Heroes
Romanian Ben 10 şi Generator Rex: Ajutoare Neaşteptate Ben 10 and Generator Rex: Unexpected Help
Russian Бен 10/Генератор Рекс: Работа в Команде Ben 10 / Generator Rex: Teamwork
Spanish (HA) Ben 10-Generador Rex: Héroes Unidos Ben 10-Generator Rex: Heroes United
Turkish Ben 10-Generator Rex Heroes United Ben 10-Generator Rex Heroes United


Voice Actor Role(s)
Yuri Lowenthal Ben Tennyson
Daryl Sabara Rex Salazar
Dee Bradley Baker Humungousaur
Big Chill
John DiMaggio Rath
Bobo Haha
Black Pawn
David Kaye Shocksquatch
Grey DeLisle Rebecca Holiday
Diane Farrah
Wally Kurth Agent Six
Jennifer Hale Black Knight
J.K. Simmons White Knight
Freddy Rodriguez Caesar Salazar
Michael Emerson Alpha


  • Ben has access to new and old aliens, placing the events of this special after Ben 10,000 Returns.
    • For Rex, this special takes place after Double Vision, as he uses his enhanced goggles. However, this special aired before Double Vision.
  • Ben claims that he goes to parallel worlds all of the time, referring to adventures to places such as Legerdomain and The Forge of Creation.
  • Caesar explains that Alpha was one of the very first nanites during the nanite project in Abysus.
  • Rex and Ben both tell their origin stories.


  • Rex's "theme song" is taken from the Ben 10 theme song of the original series.


  • Lodestar's mouth opens when the billboard starts to fall.
  • When Rex is trying to remove the nanites from Rath, Rath has dark green pupils.
  • In one scene, Rath has five fingers. Additionally, in one frame after saving Diane and her cameraman, one of Rath's eyebrows is colored white, similar to his reboot counterpart.
  • When Rex is first holding Six, his glasses are off and his eyes are closed, then when Rex tells Ben it was all his fault, Six has his glasses on.
  • When Big Chill talks to Rex after escaping captivity, the insides of Big Chill's eyes are light green and the outside is dark green.
  • In one scene, Diamondhead's head has an error.
  • Four Arms' hologram faces away from Ben.
  • In Ben's flashback:
    • One Echo Echo clone has black lips.
    • Heatblast and Stinkfly's designs were taken from the original series.
    • Goop's Anti-Gravity Projector is missing.
    • Cannonbolt's eye dashes are green.
    • Wildmutt's missing his middle teeth.
    • Big Chill's wings are missing.
    • Ripjaws has one pink eye and one green eyebrow.
    • Diamondhead's spikes are missing.
    • Ampfibian's white swipes in the middle of his body are missing.
    • Upgrade only has one line on his body.
    • Four Arms is also missing part of his body, he cuts off at XLR8's head.
    • Jetray is missing black borders around his eyes.
    • Chromastone's teeth are green rather than white.
    • Cannonbolt's white body is darker, especially compared to Echo Echo right above him.
    • Spidermonkey's eyes appear pure black, save for the green pupil, rather than having green around them in a ring.
    • Four Arms, Upgrade, and Rath are all in their Ultimate Alien designs rather than their new designs for Heroes United.
  • During the flashback, Ben says there is DNA in the Omnitrix even though he is wielding the Ultimatrix (and that the DNA is actually on Primus).
  • When Ben transforms into Big Chill for the second time, he has five fingers.
  • When Ben transforms into Upgrade, the Ultimatrix symbol is missing, and only appears when he merges with Rex.
  • When Ben reverts from quite a few aliens in this crossover, the sound of the Ultimatrix being activated and then hit down is played.


  • The episode was originally titled Gen 10.[FMS 1] This title was later used, albeit slightly modified, for Ben Gen 10.
  • Ben and Rex's conversation with Caesar on his ship was storyboarded by Fill Marc Sagadraca.[FMS 1]
  • The episode was first shown at New York Comic-Con 2011, several days before its official premiere on television.[AC 1]
  • Man of Action had thought of Ben and Rex meeting each other, from the very first day.[AC 1]
  • Unlike in Ultimate Alien, Ben does not shout the names of his aliens after transforming into them in this episode, because the writers forgot to write it.[DR 1] He also does not use any of his Ultimate forms, whereas he does so in Hero Times Two.
  • The part where Ben transforms into Rath for the second time was cut in the Asian and Polish version.
  • The Sky Slyder is the only accessible machine that Rex doesn't use in the special.
  • Duncan Rouleau considers Heroes United his favorite Ben 10 film,[DR 2] even though it is a special and not a movie.


Crew Statements

Fill Marc Sagadraca

Duncan Rouleau

Audio Commentary

Ben 10: Ultimate Alien Episodes