Andlátkyn; Vandr Sanses unin Alagaësia

It's a Strange Multiverse

"What th- the hell?!"

"Whoooaa, calm down there buddy." Outer flung his hands out in alarm.
"A twin?! Sans where-"
"I can explain!" He interrupted, slightly panicky.
"Sans, how do you explain an identical twin?!"
"Trust us, please!" Outer begged, sweating nervously.

Undyne paused, still in disbelief, before slowly squaring her shoulders and sighing.
"O..kay… Explain."
"Maybe inside?" Classic suggested cautiously.
She stared at the pair for a long moment, then bent over and grabbed both of them by the hoods, swinging them inside.
"Sorry, lookalike. You're getting the Sans treatment."
"Eheh. Don't worry, I'm used to it.."

They were promptly dumped on the couch, but before either could get a word out, Undyne was shouting up the stairs.
"Hey guys! Sans has a twin!"
After a few seconds of the two cringing, Alphys' voice exploded from her closed door. "WHAT?!"

Outer gave Classic a look as the lizard slammed open her door, glasses hanging halfway off her face and only barely balanced on her snout, swinging as Frisk appeared behind her, stoically confused.

"Sans?!"
"That's me."
"Why did you ask me about th-the Multiversal Theory?"
"What?" Undyne interrupted as both skeletons shrugged.
"I dunno, Alph. Why did I ask you about that?"

She started scrambling down the stairs. "Is this a prank y-ou're pulling again?"
Undyne grunted. "Yeah, Sans. What is this?"
He only pressed himself deeper into the couch, sighing at Frisk's expression. Outer blinked at the knowing gaze, glancing between the two- only to receive a faint nod from the original.

"So." The space themed skeleton started, since Classic wasn't opting for explanations yet.
"You look identical." Frisk stated.
"Yep."
"What's your name, by the way?" Undyne asked.
"Just call me Outer."
"He's Outer this world." Classic immediately added with a grin. Undyne groaned under her breath as Alphys blinked owlishly.

"Can I just get to the point?" The fish lady asked.
Both skeletons shrugged. She narrowed her good eye at them before pointing her hands at the two, namely Outer. "Where did you even come from? We haven't really seen.. other skeletons." She glanced suspiciously at Classic, who looked away.

"Well.. he texted you about the theory, right?" He indicated the first and the lizard.
"You're joking." Alphys deadpanned, a shocking expression on the scientist.
"For once, no."
"I don't get it." Undyne stated.

"He's from another universe like ours." Frisk murmured, not taking their gaze off the newcomer.
Undyne blinked. Shifted in place. Glanced at the pair. Blinked again.
"How?"
"Wait no, why? You seem to kn-know each other- how long have you been keeping things from us?"

Sans sighed into his hand. "I.. didn't want to tell you." The others blinked. Outer regarded him sadly, then faced the others. "He was trying to protect you."
Undyne snorted. "I don't need protection!"
"You don't know what we've seen." Outer stated severely as Sans scoffed.

After a long pause, Alphys spoke up softly. "Is this related to those.. other us?"
Outer blinked, glancing over at the first, who was quiet.
"..Yeah."
"They came here? They actually-" "How do you think Cross got half my Soul?" He retorted.
"Wait what-"
"He shouldn't have even been able to access-"
"You really believe the Soulless excuse for a guardian? Ink let them in."
"What the hell are you two talking about?" Undyne snapped their attention back to the others, staring specifically at the original Sans.

"The attack. They're talking about the attack." Frisk said quietly.
"They're-" Undyne paused, beginning to piece it together.
"How can separate universes interact in the first place? How is that even possible?" Alphys questioned without one stutter.
Now Sans just shrugged. "I have no idea."
"Actually, it's a bit of a trade secret." Outer explained, earning a glare from the original.