(A quick warning: Attack on Titan is a teenage anime, therefore, there will be some swearing. I'm trying to keep both of these shows as cannon as possible so please, pardon some of my language.)

The wind blew through the trees as a pair of twins, a boy and a girl, stepped out of a rugged, old shack and onto the front lawn. The twins, renown for their bravery against many of the paranormal creatures roaming around the town.

Dipper, the male twin flipped through his trusty, maroon journal, reading over and over again the pages of mythical creatures that he and his sister had not yet encountered, debating with himself which creature would be worthy of a find today.

"Hmm, which to choose? Eyeball bats?"

"Too creepy looking!" His sister replied, skipping alongside his brother.

"Alright, how about exploding-"

"Too explodey!"

Her brother paused, looking at his sister.

"I didn't even finish what I was saying, Mabel."

"Well, can't we just explore without that stupid book for one day, bro?"

"Wh-What?! Mabel, this book is probably the most interesting and dangerous thing that's happened to us all summer!! Do you want it to get stolen?!"

"Well, I didn't say you couldn't bring it along! I just said that I don't wanna use it today, bro bro!"

"Oh. Well, I guess,"

"Thanks Dipping Dots!" Mabel interjected, giving her brother an affectionate noogie.

Claklack claklack the horses' hooves hit the cobblestone path hard as they ran, each carrying a man or woman on one of their backs. A scream resounded as one soldier looked back, over his shoulder.

"KEEP MOVING!! THERE'S NO TIME TO LOOK BACK!"

"S-SORRY, COMMANDER LEVI!"

Levi looked back ahead and urged his horse to go faster, speeding to the front of the group and slowing down so as to run beside another commander.

"How many still alive?"

"Thirteen," Levi responded, Determination lacing his features as his short, black hair blew behind him.

"Shit...What're we gonna tell the families..."

"We'll tell them the truth, they fought for humanity. Their sacrifice will not be in vain. But, for now we must focus on getting back to the safety of wall Sheena."

The other man chuckled bitterly.

"How long are we planning to keep this up? We don't seem to be making any progress in killing them. Whenever we do another just seems to take its place."

"Patience. Wouldn't wanna go running home to your mother on the first day as commander, would we?"

The other commander stayed silent, focusing on the road ahead and ignoring his higher-up's last comment.

"Almost there. I can almost taste the potatoes!"

The sunlight had changed to a warm orange as the twins trudged through the forest. As the leaves crunched beneath their sneakers, they heard a faint whirring.

"Mabel, do you hear that?"

Mabel stopped and cupped her ear.

"Y-yeah! Let's check it out!"

As they sprinted towards the sound, a purple portal came into view, the whirring becoming louder as they approached. However, as he ran, Dipper lost his footing, the book slipping out of his hands and disappearing into the swirling void.

"NO! Mabel, we have to go after it!!"

"What? Bro, are you thinking this through? What's on the other side could be dangerous and scary!...Ugh! I hate being the smarty-pants twin!!!!"

"Sorry, sis but, that book is too important!"

"So, we're just gonna jump in unaware of what's on the other side?"

"Pretty much."

The female twin paused and then sighed, holding out her hand.

"Mystery Twins?"

"Mystery twins."

And with that, the two took a running leap into the portal, unbeknownst to them the horrors of this alternate dimension.