Ben 10/Generator Rex: Heroes United 2011

Ben 10/Generator Rex: Heroes United is a crossover episode animated in Generator Rex's art style...

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, it changes in a flash of light to become 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. The hero's battle then winds up on the Brooklyn Bridge after Rex lands a well placed punch. Diamondhead gets and changes into Lodestar, attempting to counter his opponent's metal 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 becoming Rath to save news reporter, Diane Farah while Rex saves the other civilians. Rex then literally gets the drop on Rath and once again attempts to cure him of his nanites, only for it not to work again. After attempting to explain himself, Rath decides to turn back to 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.