History WesternAnimation / Ben10GeneratorRexHeroesUnited

While the special ended on a potential SequelHook, it was ultimately never followed up on in animated form, though a sequel story was produced for issue 65 of ''Cartoon Network Action Pack''. Another crossover between the two shows -- this time set in the ''WesternAnimation/Ben102016'' universe -- aired in 2021.

At Rex's hideout, Ben is locked up in a containment unit, while Doctor Holiday explains that the creature was Nanite in origin, but somehow completely different from an E.V.O. Ben offers help but is denied, escaping into the night. They are both confronted by Caesar, who explains he created the creature, whose name is "Alpha". He created Alpha as a means of manufacturing nanites that could adapt for any scientific need, but it became unstable as it developed sentience, forcing [[MadScientist Caesar]] to banish it to another dimension. Alpha invades to absorb E.V.O.'s for their nanites, hoping to gain control of Rex's as it knows he holds the key to it obtaining perfection.

This special is Canon to both, and even introduced a new alien for Ben, Shocksquatch, that was then used in the new series ''WesternAnimation/Ben10Omniverse''. It was generally well-received by fans of both series, and has hit the top 100 on iTunes.

As this special was semi-livetroped, unmarked spoilers abound.

* ArbitrarySkepticism: With everything they've gone through, Rex is still resistant to the idea of aliens or parallel worlds. Mitigated by the the fact that (with the exception of that one CryptidEpisode) everything he's seen so far has been a result of terrestrial technology in his own dimension. Though it's worth noting that Rex did eagerly consider the possibility of alien technology while being beamed instructions for a machine in "Mixed Signals", incidentally the episode that introduced Caesar.

* AsideGlance: Holiday after Cesar takes off with the metal fragment without an explanation. She's probably talking to Six, but is looking right at the audience.

* AttackOfTheFiftyFootWhatever: [[spoiler: Alpha's final form.]]

* CasualDangerDialogue: After Alpha has just gone Heatblast:
--> '''Ben:''' Can he ''do'' that?
--> '''Rex:''' I think he just did.
--> (*''run away''*)

--> (*''Alpha has gone Four Arms''*)
--> '''Ben:''' Okay, you got to admit, that looks pretty cool. Should I try those [[YouFightLikeACow insults]] now?

* FireForgedFriends: when they first meet, Ben and Rex end up fighting each other, and keep arguing for a good part at the beginning of the story, but gradually come to become friends as the episodes goes on.
* FusionDance: Between Rex and Upgrade!Ben. This form comes complete with a super jetpack, RocketPunch (perfect for EyeScream!), MacrossMissileMassacre, a full-on [[CoolBike rocket cycle]] and improved CoolSword.
%% * GettingCrapPastThe Radar: Due to overwhelming and persistent misuse, GCPTR is on-page examples only until 01 June 2021. If you are reading this in the future, please check the trope page to make sure your example fits the current definition.

* OriginStory:
** Ben and Rex explain theirs to each other at the same time.
** Also, Alpha's origin is narrated by Ceasar.

--> '''Rex''': In case you hadn't noticed, [[TemptingFate we're holding you under house arrest]].
--> '''Ben''': *grins* You aren't holding me. I was staying so I could see how I could help. *turns into Big Chill and walks out*

* SequelHook: The special ends with many potential elements for a sequel; [[spoiler:Ben is explicitly mentioned to have been infected with nanites upon his arrival in Rex's world, Alpha is shown breaking out of his prison inside the Null Void, and Six suggests Rex and Ben could meet again at the end of the special]]. However, Generator Rex's third season ended up being its last, and the showrunner for [[WesternAnimation/Ben10Omniverse the Ben 10 installment following Ulimate]] explicitly stated he wanted nothing to do with these ideas (and never did), making this an AbortedArc.
* TheStinger: [[spoiler:Alpha is showing signs of breaking out of the nanite sphere it's trapped in]].

* TeethClenchedTeamwork: For a while.

* OffModel: Understandable, since Ben (and his aliens) were drawn by Generator Rex's art staff who weren't used to the new character designs, there are quite a few mistakes that made their way to the special:
** Lodestar is drawn with his "mouth" open in one scene, even though he technically doesn't have one because he "speaks" telepathically.
** Upgrade is drawn without his Ultimatrix symbol [[spoiler:right before Ben merges with Rex in the climax]]
** The most egregious one is probably the fact that when the Ultimatrix is activated, it always makes a certain sound, and when Ben reverts back to his human form, it makes a different sound; but throughout the entire special, whether he's going alien or human, the only sound effect that plays is the "activation" sound.
** The scene where Rex and Ben are explaining to each other their origin stories, and all of Ben's aliens are shown behind him in a single shot, one could make a drinking game of how many of them are drawn off-model.

* ArbitrarySkepticism: With everything they've gone through, Rex is still resistant to the idea of aliens or parallel worlds. Mitigated by the the fact that (with the exception of that one CryptidEpisode) everything he's seen so far has been a result of terrestrial technology in his own dimension.
** Though it's worth noting that Rex did eagerly consider the possibility of alien technology while being beamed instructions for a machine in "Mixed Signals", incidentally the episode that introduced Caesar.

* CallBack: Cannonbolt!Ben saves Rex and himself from the exploding hovercraft the same way he protected Gwen and Max from re-entry in [[{{WesternAnimation/Ben10}} the original series]].

* CardboardPrison: Pretty much anything for a guy who can pass through matter, like Ben as Big Chill. (He lampshades this by saying he could have left any time he wanted)

** MotifMerger: In the beginning, their respective logos are fused, with the Omnitrix symbol forming the hub of Rex's gear symbol. See again when Fused!Rex builds his Upgrade-enhanced PowerFist.

* OriginStory: Ben and Rex explain theirs to each other at the same time.

* WorfHadTheFlu: Six was critically injured during the initial fight with Alpha, putting him out of commission for the rest of the special.
** To a minor extent, Ben lost to Rex in their fight only because he was distracted saving civilians, and spent part of the fight with Alpha with his Ultimatrix malfunctionning.

While the special ended on a potential SequelHook, it was ultimately never followed up on. However, another crossover between the two shows -- this time set in the ''WesternAnimation/Ben102016'' universe -- aired in 2021.

* PowerCopying: Alpha manages to copy Ben's Ultimatrix, giving him versions of [[PlayingWithFire Heatblast]], [[MultiArmedAndDangerous Four Arms]] and [[EverythingsBetterWithDinosaurs Humungousaur]].

A mysterious rift begins to open in the skies of Manhattan. Meanwhile, Rex is sparring against [[TheStoic Agent Six]] while musing about his need for a "theme song," they are interrupted and sent to close the rift. Providence appears on the scene to stop the rift, but are unable to do anything before Rex arrives with Six and [[DeadpanSnarker Bobo]]. [[HotScientist Doctor Holiday]] then gets a scan that shows something is coming through the rift, and Rex finds himself (unknowingly) fighting against, [[{{WesternAnimation/Ben10}} Ben Tennyson]], in the form of Humungousaur. During their skirmish, a strange metallic creature also appears and heads into the city, with Bobo and Six on its trail. Ben is finally defeated by Rex, when trying to protect bystanders, revealing his true human form. Then, Six appears with the creature, which self-destructs and renders him comatose, leaving Rex horrified and angry at Ben.

* FastballSpecial: Rex, with Four Arms!Ben as the thrower.
** Rex returns the favor with Cannonbolt.

** Upgrade is drawn without his Omnitrix symbol [[spoiler:right before Ben merges with Rex in the climax]]
** The most egregious one is probably the fact that when the Omnitrix is activated, it always makes a certain sound, and when Ben reverts back to his human form, it makes a different sound; but throughout the entire special, whether he's going alien or human, the only sound effect that plays is the "activation" sound.

* ThemeTuneCameo: Several times, one example being when Ben transforms back to human the ''Ultimate Alien'' theme plays. The episode also has Rex trying to write his own theme song at the beginning of the episode, the result being one to the melody of the first ''WesternAnimation/{{Ben 10}}'' series.

While the special ended on a potential SequelHook, it was ultimately never followed up on. However, another crossover between the two shows -- this time set in the ''WesternAnimation/Ben102016'' universe -- is set to air in 2021.

* GettingCrapPastTheRadar: When Rex and Ben crash back to earth with Rex carried in Cannonbolt:
--> '''Rex:''' ''Ewww!!'' Do...you...have...''any'' idea what it ''smells like'' in there, dude?!
--> '''Ben:''' I'm sure you can handle a little Arborean [Pelarota] musk to save your ''nuts'' and bolts, ''dude''.

A mysterious rift begins to open in the skies of Manhattan. Meanwhile, Rex is sparring against [[TheStoic Agent Six]] While musing about his need for a "Theme song," they are interrupted and sent to close the rift. Providence appears on the scene to stop the rift, but are unable to do anything before Rex arrives with Six and [[DeadpanSnarker Bobo]]. [[HotScientist Doctor Holiday]] then gets a scan that shows something is coming through the rift, and Rex finds himself (unknowingly) fighting against, [[{{WesternAnimation/Ben10}} Ben Tennyson]], in the form of Humungousaur. During their skirmish, a strange metallic creature also appears and heads into the city, with Bobo and Six on its trail. Ben is finally defeated by Rex, when trying to protect bystanders, revealing his true human form. Then, Six appears with the creature, which self-destructs and renders him comatose, leaving Rex horrified and angry at Ben.

* ArtShift: For Ben and his aliens. They're done in the ''WesternAnimation/GeneratorRex'' (more detailed) style. This has the effect of making Ben look older.

A mysterious rift begins to open in the skies of Manhattan. Meanwhile, Rex is sparring against [[TheStoic Agent Six]] While musing about his need for a "Theme song," they are interrupted and sent to close the rift. Providence appears on the scene to stop the rift, but are unable to do anything before Rex arrives with Six and [[DeadpanSnarker Bobo]]. [[HotScientist Doctor Holiday]] then gets a scan that shows something is coming through the rift, and Rex finds himself (unknowingly) fighting against, [[{{WesternAnimation/Ben10}} Ben Tennyson]], in the form as Humungousaur. During their skirmish, a strange metallic creature also appears and heads into the city, with Bobo and Six on it's trail. Ben is finally defeated by Rex, when trying to protect bystanders, revealing his true human form. Then, Six appears with the creature, which self-destructs and renders him comatose, leaving Rex mortified and angry at Ben.

* SequelHook: The special ends with many potential elements for a sequel; [[spoiler:Ben is explicitly mentioned to have been infected with nanites upon his arrival in Rex's world, Alpha is shown breaking out of his prison inside the Null Void, and Six suggests Rex and Ben could meet again at the end of the special]]. However, Generator Rex's third season ended up being its last, and the showrunner for [[WesterAnimation/Ben10Omniverse the Ben 10 installment following Ulimate]] explicitly stated he wanted nothing to do with these ideas (and never did), making this an AbortedArc.

* ThemeTuneCameo: Several times, one example being when Ben transforms back to human the ''Ultimate Alien'' theme plays.
** At the beginning of the episode, Rex tries to create a song for himself and uses the same tune as that of ''WesternAnimation/{{Ben 10}}''.

* SequelHook: The special ends with many potential elements for a sequel; [[spoiler:Ben is explicitly mentioned to have been infected with nanites upon his arrival in Rex's world, Alpha is shown breaking out of his prison inside the Null Void, and Six suggests Rex and Ben could meet again at the end of the special]]. However...
** AbortedArc: Generator Rex has since then been cancelled, and Derrick J. Wyatt doesn't intend to use any of those {{Sequel Hook}}s.

[[quoteright:240:https://static.tvtropes.org/pmwiki/pub/images/Heroes_United_Logo_9424.png]]

* CreateYourOwnVillain: Alpha was created by Ceasar as a way to control nanites. He then sent it into the [[{{WesternAnimation/Ben10}} Null Void]] to try and get rid of it. [[NiceJobBreakingItHero Nice job sending it someplace it could get hosts, Ceasar]].