Now, allow me to tell you a story that happened a very long time ago.
Once upon a time, when the universe was new and life had just begun, a star of two colors descended to the new land to give it's power to the world and it's people. This star, that had infinite power within it, unlike anything else, was known as the Infinity Star. For generations, this star's power was shared between two kingdoms on a small planet in this universe, and people were happy. Both kingdoms, lush and plentiful from the star's power, thrived for many years to come, until...
The king of one of the kingdoms grew greedy, demanding the power of the Infinity Star be his and his alone. Of course, the other kingdom refused, demanding the power be shared equally as it always has been. The argument grew and grew, until, for the first time since the universe was born, the kingdoms declared war. The battles escalated and no end was in sight.
The greedy king only grew more vile in his attempt to take the star's power for himself. He would use lies and propaganda to sway his people to keep fighting for him. The kingdom itself soon began to loose it's lush look. The sky darkened with smoke, and trees rotted away. The only thing that grew in that kingdom was unhealthy crab grass, and all the water replaced with lava. The once lush utopia had gotten the life and energy sucked out of it as punishment for the kingdom's growing greed and violence that stained the citizen's hearts, and it showed.
Citizens of this once lively kingdom grew deformed. Once upright mushroom kingdom people began to devolve into turtle-like humanoids called koopas. Their king was the most changed of all. He could even spit fire, and the spikes on his shell didn't help his appearance. This king of koopas was the first in line of a terrible and tyrannical race to rule this dystopian kingdom. The fighting against the other kingdom still showed no signs of stopping.
Worried about the fate of the Infinity Star, the ancestors to the Mushroom Kingdom decided to seal it away, and make sure it was inaccessible to the Koopa Kingdom. Using strong metal and magic enchantments, the ancient people hid the Infinity Star in a medallion, putting it's power to sleep and sent it to the heavens of their planet, with a prophecy:
"Only two, brothers of red and green may wield the power of this great star, and after the bearer's thirty-seventh birthday, when wed to a princess or a life changing event occurs, may the Infinity Star awaken and cease the fight between kingdoms, making the bearer King of the Universe, and his brother ruler of our fair planet."
After one hundred years, the medallion returned around the neck of a young baby with a red cap. The boy's name was Mario, and he had a brother named Luigi. The brothers were found soon after being kidnapped by the current advisor to the Koopa Kingdom, Kamek. A young, blue Yoshi had rescued the brothers and brought them to the castle, where they were soon raised to be the kings they would eventually become. Mario would be wed to the princess of the Mushroom Kingdom, Peach, soon after his thirty-seventh birthday.
At least, that was what should have happened.
Angered at the fact that his arch-nemesis would soon become king of the universe, the current king of the Koopa Kingdom, Bowser, decided to intervene with fate. The fire-breathing tyrant searched every nook and cranny of his castle to find a way to stop the prophecy. At last, it came to him. A book on gods and how to gain power. There he saw it, to gain the power to stop the prophecy, Bowser would have to sell his soul to the God of Destruction. Desperate, as the day of Mario's wedding grew closer, Bowser summoned the god and made the trade. Mario would be in for a big surprize on his wedding day. Bowser no longer had care for Peach, he craved something. Destruction. Using his new-found power, Bowser would destroy everything Mario held dear, his princess, his medallion, his planet...his universe.
Things played out just as Bowser had planned. He had staged a kidnapping to lure the Mario Brothers into his masterful trap. Then, the plan was executed. Bowser changed into his new form, Black Hole Bowser, complete with deep purple wings and extended horns. Black Hole Bowser used the most powerful spell in his arsenal: A Black Hole spell to swallow up the universe. Just as the soulless king planned, Mario was taken away into the dark creation, to his doom. Though, he didn't anticipate Luigi's escape. It didn't matter. The green fool, even with the medallion Mario had given to him in his last moments wouldn't mean much.
The spell took on more than it could handle, and eventually imploded on itself. Black Hole Bowser had flown away, celebrating his victory. A new universe was born due to the explosion, leaving Luigi, now Star Luigi: King of the Universe, alone. The poor, lonely Mario Brother began to sob. Everything was gone. His home, his friends, his brother. Star Luigi began to cry loudly, calling for his brother, calls that wouldn't be answered. At least, not for a long time.
It had been about a thousand years when Star saw his brother again. The now star-eyed king had built a spaceship to travel his new kingdom, but even with the lumas he rescued and the cat who could speak, he still felt lonely. There was an empty hole in his heart, he missed his brother. The universe to him was just too quiet. How Star longed to hear his brother chattering about himself and his accomplishments again. He longed to stand in Mario's shadow again, he didn't even realize how much he'd missed it until it was finally gone. Just to see his brother's eyes again would make his heart skip with the thrill and excitement it used to have again. No... his brother was gone, dead. Mario was dead, and Star had to move on. It was the hard truth, but the younger brother just couldn't find it in himself to accept it. That's when he came back.
A voice had called Luigi's name. Star ignored it the first time, passing it off as a memory that just wouldn't die. Star felt really hot all of a sudden. The voice called his name louder. Star didn't have it in him to turn around, for he would see nothing there. The voice called Luigi's name insistently now. Star Luigi continued to pass it off, until it got annoyingly persistent. Star turned around to see his older brother's eyes. The poor brother was speechless. He was hallucinating for sure, Mario is dead and he knows it. "About time you turned around," this so-called hallucination chirped. Now Star wasn't so sure about his sanity. He inspected the figure in front of him. It was a fire ghost, spiritual flames that are born when one with a lot of heart and a flaming soul looses their life. Mario's soul, Fire Mario, was there in front of Luigi.
"B-Bro...? Is it...really you?" Star managed to utter. "Yup! It's-a-Me!" Called Fire Mario happily. The hole in Star Luigi's heart began to heal, as he embraced his brother (Making sure to make himself fireproof) immediately after that, bursting into tears. Fire Mario comforted his brother. "It's ok...don't cry...I'm here for you."
"Mario...promise me you won't ever leave again," Star sniffled. "I would never dream of it, little bro..."