\- First of all, copies are monochrome. You colored us in with care. Please, pay attention to this line.

\- If the Vessel is meant to resemble Kris, who is the Vessel if they aren't Kris? ... We have clearly seen many times, goners are their own individual person, and they can go grey at will, but this isn't exactly explained. However, it is clear that Vessel must have had an original form that isn't grey.

Why do I think December is the original form?

First of all, Kris is the protagonist. Lets pay attention to Kris' name here. Kris, obviously, is a little nickname. Their name is short for Krismas, or Christmas. It is clear that the Holidays' influenced the name... because Kris isn't Togore. Kris had a huge affiliation with the Holidays', and still does. 

But what does this have to do with Dess? Because Dess, too, is a nickname. Dess is short for December. If Dess is a copy of Kris, we'd have to draw parallels to Kris when examining Dess, right?

But there were only few parallels than anticipated.

\- Both have a strong bond with Noelle.

\- Both play instruments.

\- Both are... kind of freaks...?

\- Both are implied to be weird, kind of rowdy...

This made me want to give up on this silly theory, however, Dess' full name is "December Holiday". What is December Holiday? Well, what is the Holiday of December? Christmas, right? You see where I'm going with this, it's Kris!

Now I know what you may be saying, "No, Dess is a deer! She can't be human!" And you very well could be right, but we don't actually know for sure. For all we know, she shares another parallel with Kris...

in that they wear goat horn headbands and she wears deer antler headbands!

Makes sense right?

So far, we dont know anything about the Vessel. The Vessel has no identity. The Vessel isn't affiliated with music, the Vessel has no gender, the Vessel has no name, the Vessel has no personality... and thats what happened. 

December was the Vessel, but she was colored in with care. She was given a personality, a sense of belonging, interests, love... and then she was taken away, returning to who she originally was. A copy, a mere vessel with no identity. December is who we see in the goner maker, atleast, the parts of here.

Now, here's where the theory gets a little wacky.

We don't know how Gaster could make so many parts, but what we do know, is that... humans don't ALL look like Kris, right? Where did Gaster get so many different copies of Kris' bodies, only slightly altered?

I believe we aren't actually seeing "different" parts, we are just modifying the body slightly. It is the same part, only with slight modifications. Throughout the entirety of the character creation, there exist no severe modifications, just a change of hairstyles, a change of clothes, a swapping of legs...

We gift them an identity so unlike who December was, it's as if they weren't even there. Only few actually remember who she was! 

She was going to be our protagonist at first, but it appears that everything functions perfectly without her. She was kidnapped to be used for our Vessel, her parts strewn about, modified, but it seemed to have been discarded, because it couldn't be used for whatever reason...?

... So, in the unused code, it is heavily implied the hidden cellphone dialogue is December. But, they speak as if they have no identity, no knowledge of themselves. 

Thank you for listening to my silly theory!

Why I think Dess/December is the Vessel (THEORY+SPOILERS!)