"Breaking news at this hour. A passenger jet has crashed in the small town of Brightburn, Kansas. Details are still coming in, but there are believed to be no survivors among the 268 passengers on board. Investigators are not yet sure what caused the plane to drop suddenly from the sky and crash into this small family farm. Among the reported dead are the residents of the farmhouse, Kyle and Tori Breyer. They are survived by their 12-year-old son, Brandon", a news reporter said. Brandon was innocently sitting in the back of an ambulance, eating a cookie. No one realized that the cause of the sudden plane crash was the 12-year-old boy. However, there was one thing on his mind: world destruction. Eventually, he walked off, put on his new costume, and flew off. As days progressed, more and more of the world felt the wrath of Brandon Breyer. He then went beyond Earth and found a world unlike any other. A world with defenseless little ponies. A place called... Equestria.
Elsewhere on Earth, a flying alien that appeared to be on fire noticed a cornfield with Brightburn's symbol etched into it. The alien landed and transformed into a young boy: Benjamin Kirby Tennyson, also known as Ben 10.
"What in the world?", Ben asked himself. The symbol matched the markings he found where other dead bodies disappeared. He transformed into Grey Matter and investigated the area.
"Hmm, interesting", Grey Matter said. He transformed back into Ben.
"This definitely wasn't a normal fire. It seems as if this was caused by lasers", Ben thought to himself. "But if it was lasers, how could they have created something this big? Unless... there's a new supervillain in town." Suddenly, his Omnitrix started beeping.
In Equestria, the Mane Six and Spike were fighting Brightburn, but they were clearly outmatched. They definitely outnumbered Brightburn, but that didn't matter. "Retreat!", Twilight shouted. She and her friends attempted to run, but Brightburn used his telekinesis to prevent them from leaving. Twilight blasted magic at Brightburn, briefly blinding him and allowing the Mane Six and Spike to escape.
In the castle, the Mane Six and Spike caught their breath. Twilight then casted a spell upwards.
Back on Earth, Ben's Omnitrix was beeping like crazy. He pressed it and a transmission came through. The audio was garbled, but he was able to make out some of the audio.
"Someone help! We're (being attacked by a) being from another world! (Our) powers (are) useless against him! His telekinesis (outshines mine!)", Twilight said.
"He's stronger (than our strongest ponies)! He's invincible!", Applejack said.
"He's definitely not (willing to become a) pacifist!", Fluttershy said.
"I may be invincible, but not even (I can face off against) this guy!", Pinkie said.
"I can't out-fly him! (He's too fast!)", Rainbow Dash said.
"We need (help from) another alien, as crazy as it may sound!", Rarity said.
"(Uh, Twilight?) Who are you trying to contact?", Spike asked. The audio became much more clearer.
"Ben 10! He's from Earth!", Twilight answered.
"How do I get there?", Ben asked.
"Well, where are you right now?", Twilight asked in response.
"Brightburn, Kansas", Ben answered. The next thing he knew, Ben started glowing. He disappeared in a flash of white.
In the castle, Ben reappeared in front of the ponies. "What the... who are you?", he asked. After the ponies and Spike introduced themselves to Ben, the castle shook. Ben looked outside. "A kid? That's who's causing you trouble? This'll be easy." He transformed into Heatblast and flew towards Brightburn. The young supervillain turned to face the flaming alien.
"And what are you supposed to be?", Brightburn asked.
"I am Ben Tennyson, galactic superhero", Heatblast answered. After hearing the word "superhero", however, Brightburn immediately delivered a powerful punch, sending Heatblast flying backwards. "Whoa! Someone's cranky." Brightburn flew circles around Heatblast at a supersonic speed. In response, Ben transformed into XLR8 and tackled Brightburn at a supersonic speed.
"Okay, kid. Let's stop this before someone gets hurt", XLR8 said. Brightburn unleashed his heat vision on the young superhero, causing XLR8 to scream in pain. While XLR8 was blinded, Brightburn used his quick attacks to defeat his opponent. Before he could finish the job, however, Twilight blasted Brightburn with some magic. XLR8 transformed back into Ben.
"Run!", Twilight shouted. Ben ran into the castle.
"Pathetic fools", Brightburn said. Twilight flew into the castle, but Brightburn began to destroy it. Unbeknownst to him, however, a flash of purple light indicated that the ponies, Spike, and Ben all teleported away.
After the castle was destroyed, Brightburn looked through the rubble, but he couldn't find the individuals who escaped. "Damn it!", Brightburn angrily said.
Deep in the Everfree Forest, the heroes reappeared.
"Is everyone okay?", Ben asked. He overheard the Mane Six singing Let The Rainbow Remind You for some reason, but at least it was an indication that they were still alive.
Each one of us has something special
That makes us different, that makes us rare
We have a light that shines within us
That we were always meant to share
And when we come together
Combine the light that shines within
There is nothing we can't do
There is no battle we can't win
When we come together
There'll be a star to guide the way
It's inside us every day
See it now! See it now!
Let the rainbow remind you
That together we will always shine
Let the rainbow remind you
That forever this will be our time
Let the rainbow remind you
That together we will always shine
"I take it you guys are still alive", Ben said as Spike flew over. "Who... is that guy?"
"We don't know. All he said was yychhagaro larum ghhol, but I don't know what that means", Twilight answered.
"It means take the world", Ben said. "If he said that, then we're dealing with Brandon Breyer, otherwise known as Brightburn, Son of Darkness, an alien supervillain hellbent on destroying Earth... which is where I'm from. But... why is he here?"