I know I've been recommending like crazy, but I have one more for awhile. Human AU Toriel and Sans?
Human Sans: What the-!
Sans: Many AU's! * uses magic to pull bith humans back into the portal drom which they came*
Frisk: Was that human you and mom?
Sans: Yeah pretty weird right?
Frisk: He was hot...
Sans: *eye flickers blue* What was that Frisky?
Frisk: N-nothing!
Sans: I'm the one and only Sans you need. *kisses frisk roughly on her lips*
Frisk: ...geez...*blushes all over*