Pillartale! Where everyone's a pillar! XD Ok, jokes aside, I honestly think King Asgore would have a CHANCE of showing up for the bros; everyone in the game talks fondly about him as if he does mingle with the people a lot. Papyrus is clearly familiar with him, judging by his dialog after you defeat him in Neutral/Pacifist route. And Sans's Judgment Hall is VERY close to him. And the Santa thing. I'm sure the Flowey threat would have been major news, so the King might check on the town's savior.
Oh gdi, stop giving me ideas! XD this epilogue’ epilogues will never end!