Authors: "1850, ???, Gramparson, Sumin"
Geno is a Sans from another timeline who injected himself with Determination in Alphys's True Lab to hijack the resets, and now can retain memory for the other Sanses to use, though he himself is stuck in the void with Frisk. He is a main supporting role on Aftertale.
Note: The colors are misaligned on purpose to represent that he still has his glitchy effects from being in the Game Over Screen, just like in the comics.