Favorite undertale theories ???

Gotta be Sans' Blood, heh.

As everyone knyows, Sans, the cosmic anomaly in the world of Undertale, a character shrouded in mystery and nonchalance, at the end of the Genocide Route unveils a peculiar detail — he bleeds, unlike any other monster in the game. Quite literally, NOBODY bleeds. Not even Undyne or Toriel when slashed. Even his own BROTHER, I remind you, when decapitated, has no blood. In a universe where blood remains absent even in the face of decapitation, Sans stands as the exception, a cosmic joke woven into the fabric of his existence.

Now, now, there are many theories about why this happens, but none of them have been confirmed by the game's creator, Toby Fox. One theory is that his blood is, in fact, ketchup, which holds a certain charm, hidden in his jacket, or was consumed. I actually like this theory, but, heres the thing, he doesn't consume it that regularly, to the point of having it on him. He isn't even a fan of it, he just likes it. Now, the reason I like this one, i'll point it out at the end of my analysis. Also, Toby Fox jokingly said it was the truth, so... Fine I guess? Gotta say, The beauty lies not in the truth but in the playful ambiguity that keeps fans guessing, Nya. Then again, it has a lot of issues. Monster food is supposed to be converted into energy when consumed, so it should not leak out of Sans' body if it was like, he ate ketchup and then got killed.

Another theory suggests that Sans' blood is actually the marrow inside his bones, which also contains blood, to which at the moment of the slash somehow cuts the marrow..? I don't really see a way, its just way too precise, and believe me, I've seen some lucky coincidences!!! However, remind you, none of these theories have been confirmed by the game's creator, Toby Fox. It remains a mystery why Sans bleeds at the end of the Genocide Route. Personally, I prefer...


Sans bleeds as a lazy last effort joke or prank to make the player feel guilty.

Yep. Although it doesn't explain the blood on his mouth, its pretty much his purpose, joke around, make you feel guilty about your own actions, and let you know you've gone too far. As we all know, Sans hides behind his jokes and 'simpleness'. Maybe Sans just has a hidden device or mechanism in his jacket, which sprays or squirts blood when he is killed. Of course it would require good engineering skills, but remember he was a scientist himself, and he used to experiment, so far as realizing and remembering Timeskips and deaths. Even Timelines. He is no normal skeleton. This is a pretty lazy explanation, but remember, who are we talking about, hm? Lazybones. As for the blood on his mouth, he may have just literally exploded the ketchup, and we wouldn't even know because he covers almost his entire damn body. He could've literally made it so it explodes inside his torso, and reaches inside his skull through the ketchup burst.


Honestly, I don't think we'll get any answer, but god dang it, Susie does say in deltarune chapter 1 that everybody bleeds, then the guy in that one house asks Kris if he bleeds!! (you know, only humans bleed) Would that even suggest Lightners DO bleed??? Is SANS A LIGHTNER-


Anyways, I'll go rest well in the shadows, where dreams dance like chaos in the moonlight. Goodbye, nya.

Sans is Ness.