What a curious world." Buu hummed thoughtfully to himself. It had been years since he was released on Earth and defeated and absorbed everyone on that planet, adding all their power to himself.
From the mighty Gohan, the intelligent Piccolo. Even those interesting androids that bestowed upon him infinite energy had not escaped being turned into food and devoured by him.
For years he had scoured the galaxy for new worlds, devouring the populations of those worlds and adding their power and abilities to his own. Even the destroyer Beerus fell before his might.
And now, he found himself overlooking a new world, one with spiritual energy combined with their physical energy, their ki. Potent abilities as far as the eye could see!
A world of ninja!
A smile curled across Buu's lips as he began to descend towards the planet in question. A whole new world to eat and gain power from. He couldn't wait to get started.
The ninja of the Hidden Leaf Village would soon know the terror of Majin Buu.
His senses locked upon a white man as he descended, training with three children. Two boys, blonde and black haired, while there was a girl with an exquisite shade of pink hair, much like his own glorious pink form.
Time to announce himself and strike the terror of Buu into their hearts!
He dropped from the air and landed amongst them, spreading his sublimely pink arms wide open, "Behold mortals, Buu has arr-"
He never got to finish as a shout of "Tajuu Kage bunshin no jutsu!" cut him off.
And a wave of monstrous diminutive blonde haired children in orange descended upon him, much too fast for his pitifully sublime self to react to.
"Eeeeek!" Buu squealed like a little girl as they began beating the crap out of him, "Stop it! Please! Buu sorry!"
But they did not.
"Katon: gokakyu no jutsu!" another shout followed after the mass of blonde children were done beating the shit out of him.
And Buu learned what it meant to be afraid of the ninja of the Hidden Leaf Village. As he was burned to death, like the pathetic pathetic beta bubblegum bitch he was. Not even all the power of the Z-fighters and Lord Beerus combined was enough for him to stand up to the might of some genin.
An alternate timeline. And yes, this would be Zen Buu.
But no matter how Zen Buu is, he's still just a Buu.
Youth!