I love how linked the Yellow and Blue souls have been even before Deltarune. They pair up to sing during Finale in Undertale The Musical(they also somehow paired up aqua and purple, and green and orange. How tf did they guess all three duos correctly in like 2016????).
In Undertale Yellow the integrity human is extremely important to the plot.
The two colors in Sans' eye being blue and yellow. There's probably more that im missing And now we have them officially together in Deltarune, with duzens of fanarts depicting the two of them falling together into the underground They're together in every universe, even before we knew it
