A/N: I came with this exact AU near the end of 2019. If you want to know more about its concept and a few of the Shroob OCs as mentioned later in this story, please visit 'successfullyshroobifiedsmbau' on Tumblr. Enjoy reading this :)
I hope you know how the story goes? *chuckles* I'll be telling it in a nutshell.
Long ago, the alien species known as Shroobs invaded the Mushroom Kingdom of the past since their home planet was at the verge of going extinct, and they needed a new place to live despite not all of them being able to speak any English. (Don't worry, I subtitled all of the upcoming Shroob language in this fanfic for your convenience, because of course barely any human can understand it. *chuckle*)
This caused some ruckus among both the baby Mario brothers, who resided in the past, and the adult Mario brothers, who resided in the present. They met up in Hollijolli Village in the past, and again at Baby Bowser's Castle, also in the past, where they officially became a team.
Clues about the Shroobs, who had kidnapped the adult princess Peach and kept her prisoner somewhere, were frantically sought in the following locations of the Mushroom Kingdom of the past: Toadwood Forest, Yoshi's Island, Gritzy Desert, Thwomp Volcano, Toad Town, Star Hill, and what is now known as Shroob Castle, rather than princess Peach's castle in the past.
However, things went dramatically wrong once the two pairs of Mario brothers had arrived at the Shroob Castle, and why, you wonder? That's what I'll be telling you now.
The Shroobs had now managed to invade a majority of the Mushroom Kingdom. About one-third of them had become wounded or even succumbed at the hands, feet, hammers, Fire Flowers and all that jazz of the two pairs of Mario brothers in the meantime, forcing the remaining two-third to go into hiding to remain safe. Dozens to a few hundreds of secret funerals were held among the Shroobs, and they were absolutely devastated to have lost family, friends, acquaintances and such to those nasty humans who had messed with their plans, which caused them to secretly plot even more than any human would've thought. Yes, even the mere kindergarten-aged Shroobs who thought that an anti-human circle and similar tactics would actually work!
Meanwhile, the two pairs of Mario brothers, as well as their anthropomorphic suitcase companion Stuffwell, had arrived at the utmost top of the Shroob Castle, where they thought they were about to save princess Peach. The adult one, that is.
Stuffwell told me, the person playing the game, to save at first for the sake of the adult princess Peach.
Well, alright, I thought, and I did as I was told. Man, how such a little adorable suitcase could actually be that strict! But alright, after saving my progress, the brothers boarded some sort of secret spaceship that they used to knock out the Shroob Mother Ship and some of Princess Shroob's lackeys who guarded the air in their UFOs.
With only one point of fuel left, the two groups of Mario brothers succeeded, and the Shroobs were a few dozens of funerals richer as well. Also, the Shroob Mother Ship remained intact despite crashing upon its defeat, but the crash did cause some electric fuses to blow, freeing princess Peach from the barricade in which she was trapped.
After this whole happening, I saved once more, only for things to take a very drastic turn…
Princess Peach, who had promised to wait in the spot of her barricade, suddenly wasn't present anymore.
"Princess!" the adult Mario brothers shouted. "Princess Peeeaaach! Where are you?!"
"Pwincess!" the baby Mario brothers copied them.
"Wherefore art thou?" Stuffwell somewhat mockingly added.
Little did the suitcase know, however, that I was literally laughing at him so hard that I bent 90 degrees over my Wii U GamePad in a jolting fashion because of it. But alright, enough about me, this is all about the Mario brothers.
The group was soon interrupted by some ruckus that came from the crashed Shroob Mother Ship, and they decided to investigate a little. It took them a while before Princess Shroob had apparently caught their attention. She went towards them in her hyper-modern floating throne, and she smiled so menacingly that she startled the baby Mario brothers that way.
"So" she chuckled in somewhat broken English, "you've come here to save that poor excuse of a princess of yours, huh?"
The two pairs of Mario brothers nodded.
"Well, too bad."
"How so?" Mario asked.
"You… you guys…" The alien princess burst out in maniacal laughter, and then said something that somewhat sounded like a broken "Omae wa mou shindeiru!" to the ears of us humans.
"What?"
"I said, you guys are already dead! We the Shroobs have already completely taken over the measly Mushroom Kingdom of the past without any of your knowledge! Soon, us Shroobs will finally dance on the buried remains of this pathetic kingdom!" She facepalmed and groaned. "Goody, you guys are as unintelligent as drunken Snoozorbs…!"
"Mama Mia!" the adult Mario brothers shouted. "We're done for!"
The baby Mario brothers, however, still didn't seem to understand what all of the ruckus was.
"We're no longer safe…" Stuffwell whispered to them. "I simpleasily have no clue what to do now…! We're doomed!"
The infant brothers were especially struck hard by the tone in which it was explained, and they started weeping in a heart-shattering fashion.
"Now go back to the present and stay there!" Princess Shroob shouted, "or else I'm going to destroy you lot! And don't even think of sending that Bowser guy here, because he'll also be destroyed if you do!" Her tone scared the poor baby Mario brothers even more.
"But what are you going to do with princess Peach?" Mario tried.
"I'll simply interrogate her, but that doesn't mean you'll be getting her back…! Unless you come with some silly plan that won't work anyway despite all of the effort you've put into it. Any more questions?"
The two adult Mario brothers, who tried hard to console their baby selves, shook their heads.
"Then begone."
The two pairs of Mario brothers and Stuffwell did as they were told.
"Oh my Globin" Stuffwell groaned in disapproval. "Never knew it'd end like this. We're doomed, and we cannot do a tidbit about it!"
"At least we're still safe in the present" Luigi said.
"And little do they know that they won't be getting that silly Junior Shrooboid of theirs back either…!" Mario whispered somewhat menacingly. "Especially not if we won't get Peach back."
"Good point."
The group soon found their way back to the time hole, and stepped into it, despite totally not being prepared to tell their friends and acquaintances about the bad news. Little did they know, however, that their collected parts of the Cobalt Star were suddenly gone, too…!
It remained quiet in the room where Princess Shroob found herself, until the sound of teeny tiny footsteps was heard near her. They came from little Pit, her favourite servant. They were a 'regular' kind of Shroob (what I call the oft-seen purple ones), and despite only being of kindergarten age, they were already as intelligent as Professor Gadd, just except for the fact that Pit simply wasn't able to invent anything because they were a bit clumsy with their hands and maths.
"Good newth!" they enthusiastically lisped through their loose front teeth. "I intewwogated the pwintheth a wittle, and even managed thoo pickpocket hah!" They showed the last Cobalt Star part that the Mario brothers still needed from their princess.
"I praise you for a full hundred per cent, Pit" Princess Shroob kindly said with a smile as she patted her young servant's head. "Now, is that the only part that you have?" She asked this in a somewhat stricter tone.
"No, ma'am. I awtho pickpocketed the human bwothahth when they wewen't wooking! Pwethiouth woot!" The intelligent kindergartner got the five points of the same star from their snag bag and also showed them.
"Oh my goodness, amazing job you did there! This'll surely set my sister free!"
"Wait, you thtill owe-"
"But not before I told the rest of our kind about the good news, of course!" The alien princess's enthusiasm then dissipated just as quickly. "Oh… and also not before telling certain people that they've lost someone once again. Stupid mushroom brain excuses of humans…"
"I'm thowwy fo' the famiwieth that lotht them yet again… thend them my condowentheth…" Pit couldn't help but tear up a little.
"I surely will, darling." Princess Shroob got a handkerchief from her chest pocket and dabbed at the sides of her servant's eyes with it. "Now, why won't you rest and tell Clyde that he's in charge of me now? After all, you deserved it after serving me non-stop lately, you poor little creature."
"Thankth, I will, pwintheth." And with that, the little servant went off with their same tiny footsteps.
And this was only just the start of the newly-established Shroob Kingdom.