So, I've seen stuff like this done in other oneshot books, and I just had to hop on the bandwagon XD

Setting: Season 6

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(Dimension: FoF)

Grian stared at his hand, trying to make a ball of light appear on it. After some concentration, he managed to get a faint sphere to appear, but nothing bright.

He groaned, leaning back and lying down on the floor of his secret lab. He was trying to learn magic other than the glamour, but it was surprisingly difficult.

He was just about to close the book next to him when a portal opened underneath him, dumping him onto someone, someone with his same sweater.

(Dimension: Mermaid AU)

Grian absentmindedly swam along the edge of the reef, admiring the trench just beyond. Of course, it was a bit forbidden to dive into the trench, because of the undertow caused by the sizzling magma and volcanic activity below, so Grian didn't dare get too close.

But the view was still captivating, the sizzling orange amongst the dark greys, bubbles escaping up only to be yanked back down by the undertow.

Grian's thought's were interrupted by a portal that dragged him through a sea of light blue magic, dumping him in somewhere dry and humid.

(Dimension: Highschool AU)

Grian tucked his sweater under his arm as he sprinted away from Iskall, laughing. Mumbo wasn't far behind. They'd engaged in a friendly game of tag, and Iskall was it.

But when Grian rounded the corner, he discovered nothing under his feet, and fell through the portal with a shriek.

(Dimension: Genderswap AU)

Grian tied her messy hair back in a ponytail as she got to work on her mega-base, this time tidying up the pillars that ran along her base, checking for any stray concrete powder.

As she scaled the tower, she noticed a strange portal that had appeared on one of the pillars and made her way to investigate. However, once she got close, it sucked her in, dropping her somewhere vaguely familiar.

(Dimension: Roleswap AU)

Grian rolled up the sleeves of his blue sweater as he worked on the redstone. He heard someone swoop in and land smoothly with an excited "Grian!"

Grian smiled and turned around to see his fellow Architect, and CEO, Mumbo. He lived just next door, his incredible build showing off his building skills. Grian on the other hand, was really a redstone guy.

"What's up Mumb-" Grian was cut off as a portal opened under him, dropping him into a mass of light blue particles.

(Dimension: Hermitcraft)

Grian was double checking his lighting on the outer ring of his base when it happened. A portal opened above him, dumping a blur of feathers on him.

The person panicked, and as they turned around, Grian freaked out as well. This new person looked almost exactly like him, wearing a similar red sweater as well, He also had the hippie beads and flower crown on. What was different was his pointed ears, huge lilac wings, and horns.

"Who are-" Grian wasn't able to finish his sentence as another Grian look-a-like tumbled out of the portal. This one wore a school uniform and had his own red sweater tucked under his arm.

Not long after, a merman fell out, immediately gasping for water. Grian quickly broke a hole in his outer ring and pushed the look-a-like Merman into the water. He had the stereo-typical water nymph ears and a long, cream and red tail.

A couple seconds later, a girl fell out of the portal, looking basically like a female version of him.

Then finally, another Grian fell out, this one with a blue sweater, before the portal closed.

The six Grians all glanced at each other in confusion.

The Grian with the blue sweater was the first to speak. "Judging by our appearances, I'm assuming everyone here is named Grian, so we should probably get nicknames."

The Grians nodded. The winged Grian spoke up. "I'll be Fae, since well, I'm a faerie." He sounded a bit shaken up.

The Merman Grian spoke up next. "Uh, Cod boy I guess, since that's a nickname I've got back home."

Female him was next. "I guess I'll go by Gria."

The schoolboy was next. "I'll be Green, since I'm running out of ideas."

Grian blinked. "I guess I'll just be Grian, since we're all in my universe."

The Grian in the blue sweater nodded. "I'll be Blue, since I'm the only one with a blue sweater."

"So, I guess I should grab Xisuma?" Grian said before awkwardly speeding off on his Elytra.

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Mumbo landed on the outer ring of Grian's base, looking for the small gremlin. He heard a couple muffled gasps to his right, and glanced over to see the source.

He was not expecting to see five Grians staring back at him, all different in some way.

"Grian, did... Did you mess around in Area 77 or something?" He asked, his voice coming out in a confused squeak.

One of the Grians, the one that was female, spoke. "Uh... We're all from different universes and got dumped here by some portal. Your Grian is grabbing Xisuma."

"Oh-okay." Mumbo was still in shock.

"Can someone explain where we are?" the Grian in a school uniform asked.

"Yeah, I was wondering that too." said The Grian in the water. From Mumbo's perspective, he was simply shirtless, which did confuse Mumbo a bit.

"We're at a version of a season 6 Grian base." The Grian in the blue sweater explained.

"Maybe we should introduce ourselves to Mumbo?" The winged Grian suggested. "I'll go first." He approached Mumbo nervously. "Um... You can call me Fae, since I'm a faerie."

"I'm Gria." The female said. The other Grian's followed suit, ending with the Grian in the water.

He looked the most nervous out of all of them "You can call me Cod boy, or CB if you wish."

"Cod Boy?" Mumbo wondered out loud.

CB nodded. "It's a nickname I have back home."

Mumbo then noticed the nymph ears and put two and two together. "...You're a merman?"

"Last I checked. It's weird seeing so many land dwellers." CB laughed nervously.

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Grian swooped down, Xisuma behind him. He got a bit worried when he spotted Mumbo speaking with the other Grians, but relaxed when he saw no hostility or confusion.

"Mumbooooo!" He chirped, landing right next to him. Mumbo yelped, then tripped over his feet, falling on his side.

"Ow..." He muttered.

Grian noticed Mumbo exchange looks with Blue like You too? 

"That is... A lot of Grian." Xisuma said glancing around at all the Grians. A weird silence fell over them all, before being broken by Gria.

"It's so weird, being around so many guys." She said, frowning. "Back at my home, almost all of us are girls, with the exception of False, Stress, and Cleo."

"It's so weird being around land-dwellers in general." CB muttered in response.

"Everyone's personality is backwards for me." Blue added.

"Well, there's no school, so I guess that's a plus." Green chimed in.

Grian glanced at Xisuma, looking for answers, but the Admin was clueless, pulling up his screens to assess the new players. "I honestly don't know what to do." He confessed. Just then, a message appeared on one of the screens, and he let out a laugh. "Oh, I see now."

"Well, what does it say?" Grian asked.

Xisuma read the message. "The Grians are now open for Asks."

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Feel free to comment different scenarios and asks in the comments!