Frisk bounced with excitement as they and Toriel led their four new friends into the park near the center of New New Home (the final place Asgore would ever be allowed to name). The scientists trailed aimlessly behind, each eager to take in as much of the surface as they could. Frisk gasped and pointed eagerly at the small crowd already gathered near one of the picnic benches.

"Yes, my child, it seems several of our friends have already arrived."

Toriel's comment grabbed the attention of the scientists, especially of the tall skeleton with large, dark cracks on his skull. "Goodness, it's been so long since I last spoke with his majesty."

"He has given up that title," Toriel replied a little frostily.

"Yes, of course."

Frisk had already run over to give Undyne and Alphys big hugs.

"Well howdy," Asgore greeted cheerfully as the rest of the group approached. "I don't believe we've… wait..." He squinted at the four scientists for a moment before his recognition lit up his face and a large, beaming smile spread across his cheeks. "Dr. Gaster! It's been… goodness I'm not even sure! So good to see you again."

"Hello, your majesty."

"Oh, it's just Asgore now," the burly monster replied jovially as he reached out to shake Gaster's hand.

"Who're they?" Undyne asked as Gaster and Asgore fell into a friendly conversation, mostly Gaster explaining his sudden disappearance from reality and Frisk's heroic rescue.

"The lost royal scientist," Frisk replied with a grin. "And some other scientists, and a kid who somehow got lost in the void. No one could remember them because they were all in the void but I rescued them anyway!"

"Well that's just great, you did real good!" Undyne picked Frisk up for a congratulatory noogie.

"W-w-we should be able to help you all contact your f-families, if you want." Alphys smiled as she approached the other three scientists, who were still taking in everything around them in wonder.

"I can't wait until Sans and Papyrus get here," Frisk said as they bounced in place, "I think Gaster's their dad!"

"Do you really believe that, my child?" Toriel asked skeptically as Undyne looked the skeleton over. "He does not resemble either of them very much..."

"dings?!" Everyone's head turned towards the unexpected shout, only looking up in time to see a mass of faded blue collide with Gaster's side. "are you real? i'm not hallucinating you, right?" Sans's hood, which seemed to have been flipped up by his unusually fast movements, slipped down to show Sans looking rather frantic as he gripped the taller skeleton's clothes.

"Yes Sans, I'm real. You're not hallucinating, I'm so sorr-" Gaster's apology was abruptly cut off as Sans's grip shifted to better pull him down for a passionate kiss, cyan magic sparking between their teeth. Gaster's eyes widened in surprise, then drifted closed as his hands moved to the back of Sans's skull and back, cobalt magic began mixing with the cyan.

"Oh my!" Toriel exclaimed as she covered Frisk's eyes with a great, furry paw.

"I think we should give them a minute before we go say hello to Sans," one of the scientists said indulgently to the others, who all nodded in agreement.

"What the fuuuuuu..." a glare from Toriel was the only warning Undyne needed to change her curse at the last second, "...uuuudge?"

"I do believe," Toriel said while trying to hold back a laugh, "that Dr. Gaster is not Sans's and Papryus's father after all."

This little tidbit is actually part of a larger story that I'm not sure I'll ever be able to write because it's pretty incomplete. It's like having a 1000 piece jigsaw puzzle with only half the pieces, there's half a park bench over here, a tree over there, and that cluster's one of the corners… so here, have the half a park bench.

I'm really enjoying Entropy by talkingsoup over on AO3, specifically the idea that when Gaster was lost and Sans was the only one left with memories of the original timeline that it took a lot of adjusting on Sans's part. So if I ever did write out the rest of this Sans would basically have spent a few years being gaslighted by reality, at least until he found some concrete proof that something had happened.