Well, Mat was the Youtube that made me want to start theorizing about games, so usually I idolize him and buy everything he sells, but I do try to put under the light all of his theories and find minor details that he might have overlooked, and this time I’m not 100% convinced of his theory. I must admit that I didn’t noticed that little detail you mentioned as so far I’ve never gone to Sans workshop (everytime I do a pacifist I’m so excited to fight Asgore that I forget to reset to get Sans’ Key. Asgore’s battle intro is so damn epic that I fanboy a little and just want to get there quick :P). You are right, if Sans became... well, Sans before the photo was taken, there’s no way the photo is the same as the one from Earthbound.
Funny fact: I haven’t finished Earthbound yet, I literally began playing it for the first time last Saturday. I’ve been the last 20 years spoilers free from Earthbound and that vid spoiled the shit out of me with no warning :I
Instead, I do think is a minor easter egg, but I won’t say anything else about the pic cause my next post is a list of all the Earthbound references that I noticed when I started playing it the other day, and I don’t want to spoil it ;P
Back to your question, the Game Theory still has some things I don’t think are solid enough to say that Sans is indeed Ness.
For example: I don’t believe Papyrus is a Starman. They say that they made that suit for a Halloween party and that Papyrus hasn’t take it off since. Maybe they found a Starman dead body that was transported there somehow.
Another thing, I will never believe that Sans and Papyrus appeared one day in Snowdin cause they simply spawned there. Most people takes too literal what the old bunny lady says: “they just showed up one day and ... asserted themselves”. If we think about the headcannon that Sans and Papyrus are Gaster’s children we could think this: Sans and Papyrus lost his father when Papyrus was young and Sans had to look after him. If Gaster was the royal scientist maybe he used to live at the Capital. When he... “passed away”, Sans and Papyrus grew up in there, probably Asgore took care of them. Sans became a royal scientist like his father and Papyrus saw the Royal Guards and wanted to be one too. Then, recalling the Sans’ theories a few post under this one, if he injected himself with DT and needed rest he went to Snowdin with his brother, that way, if something went wrong, the side damage would be less than if he was at the capital. He told Papyrus they were there for training or patrolling and thanks to his brother innocence they just established there. They probably had spare money from Sans salary as a Royal Scientist or maybe Alphys gave him that money from some kind of funds Asgore gave her for her researches. The thing is that they indeed moved there, as the Hamster dude (he looks like a horse for me) from Grillby’s says that the people from the Capital is moving there. Probably he was making reference to the skeletons.
And finally, Sans knowing what the sun is... I really was like “really? is that evidence for this theory?”. Sans has a physics book-ception in the table next to his sofa. He knows a thing or two about physics and certainly he read about the Sun in one of his books. How Sun’s light travel through space is one of the first examples they give you when learning about electromagnetic waves.
Sans’ magic is no mystery. If he was Ness, Ness can use Psy. If that’s not the reason, when he became a monster, he gained the ability to use magic the same way Dummy, Blooky and Mettaton when they became ghosts.
Well, I think I talked a lot about the theory xD
To sum up: I liked the Theory just cause it’s Mat Pat’s theory, but I didn’t actually buy it. Now, thanks to your contribution with that hole, I could realize I like it cause it’s a nice headcannon and points out lots of Earthbound’s references and Easter Eggs Toby put there but in the end is just that, another headcannon. In the other hand, I love and totally support Gaijin Goomba when talking about UT Irish roots. If you haven’t watched them don’t lose time and watch them now!!!