Theory - Who Are the Fallen Humans?

According to the shopkeeper in Snowdin, the two skeletons Sans and Papyrus appeared out of nowhere. Monster Kid is also unsure of their age. In Deltarune, although everyone is seemingly older, Sans still asks us if we can "babysit" Papyrus for him.

Napstablook is depressed yet perseverant, Papyrus, though childish, is kind, Mettaton has extreme integrity, despite being slightly egotistical and Sans serves justice in Genocide (he also creeps us out in certain phone calls in the Neutral routes). Sans is also known to 'watch over us' and keep track of our LV and EXP. Ghosts and skeletons represent the undead. In folklore, they are what was once alive that had died and been resurrected again (similar to what happened with the Amalgamates).

We know that human souls are extremely powerful and all traits have a form of Determination, the most powerful factor in the game. This powerful magic could allow for the fallen humans to come back to life after death (note that Alphys injected Fallen monsters with Determination which caused them to continue to live, though you could argue that they weren't exactly dead).

It has also come to my attention that the fallen humans' souls are in seemingly perfect conditions in Asgore's containers in the Barrier room.

The Omega Flowey fight is an important part of this theory, since we fight with the souls. The light blue soul throws knives at us. This is interesting since Mad Dummy's last resort in their fight is a knife. The orange soul's attack "uses rings of hands that move around the screen downward". These hands have holes in the middle and if you pay close attention to the music played during this fight, it sounds a bit like Gaster's Theme (it is also important to pay attention to the music in the fights with the other souls). The dark blue soul has stars and dazzle and dancing and shoes and you see where I'm getting at, don't you (the track that plays during this SOUL fight also sounds similar to the battle theme that plays when fighting King Checker, who is supposed to make fun of Mettaton's legs)? The purple soul's attacks consist of negative words that will probably make you feel like trash (the music also sounds a bit like Ghost Fight and Chill). The green soul attacks you with frying pans that fling fire at you. The yellow soul attacks you with a gun that shoots bullets at you. The music played in the background sounds a bit like Undertale and yellow is the soul that brings all of the souls together. The yellow soul is the last soul you face before justice is served to Omega Flowey. When you use the ACT button, it instead shoots four-leaf clovers that heal you. Four-leaf clovers symbolize good luck, which is the opposite of bad karma.

This theory was inspired by this video - https://youtu.be/c0kKszy5JX0.

Thank you for checking out my theory! Perhaps I might get more information in the next chapters of Deltarune.