Just... Nate as Frisk/Natemare as Chara.
Dookie and Matt as Sans and Papyrus respectively.
Morgan as Toriel maybe?
Idk all I can think of is Nate/Natemare as Frisk/Chara.
But I can totally imagine Dookie standing in judgement of the kid that used to be his friend.
"You're gonna have a bad time~"
