So, I am starting this "series" with Sans and Papyrus. I am going to talk about where Sans and Papyrus came from and, what I believe to be their connection to W. D. Gaster.
So, I'm going to start this off with where did Sans and Papyrus come from? The only real knowledge we really get in the game is from the shop bunny lady. She tells us that the skele-bros, "just showed up one day and... asserted themselves." I am also adding to this evidence, the drawing that you can find in Sans mini lab behind the house. It is a drawing of three people and it says on the picture, "Don't forget". I believe that the three people are, Sans, Papyrus, and Gaster.
I believe that the third person is Gaster due to the fact that there are blueprints that have writing that's in "strange symbols". I think that those symbols is Wing Dings. Also, if you do some hacking into Undertale, that one sign in the true lab that's in the power room, I who I to believe is Gaster, writes "ENTRY NUMBER SEVENTEEN, DARK, DARKER,YET DARKER, THE DARKNESS KEEPS GROWING, THE SHADOWS CUTTING DEEPER, PHOTON READINGS NEGATIVE, THIS NEXT EXPERIMENT, SEEMS, VERY, VERY, INTERESTING... WHAT DO YOU TWO THINK?"
The key reason I am mention this entry is because Gaster puts in his entry, "What do you two think?" Hey word, "two". I have a theory that he may be referring to Sans and Alphys in this insert. We have proof that sans would have this type of knowledge to be a scientist because of his Joke, and Psychics book, his lab, and that he has knowledge of the timelines. I also am taking this notice a bit from Game Theorists that the entries in the true lab are written by two separate people, Sans and Alphys.
Back to what the shop bunny says about them "appearing" I think that Gaster "created" Sans and Papyrus. I think tat they where involved in Gasters research about artificial souls. I think sans and papyrus where two souls that where created successful with determination. When you l0ook at Gasters sprite, you see that he has two holes cut into his hands. I think he used samples from his own hands to create them. That would explain why the bros just appeared. It would also explain why Sans bleeds when you kill him in the Genocide route. This would also explain that throughout the game that Papyrus shows signs of determination. He is determined to see the kindness in everyone.
In my part 2 of this theory (due to the fact that I still have a bunch of this to explain) I will get more in depth with Gaster and Sans lab.
Please tell me if I have left any notes out and if you want me to add any in the next part.