Breakfasttale Sans:
Introduction: If you hadn't noticed, he is based off of a stack of pancakes. For obvious reasons, that I simply will not explain.
Most of his changes come in his jacket, made to look more puffy to resemble a stack of pancakes; I also thought it would be funny to make his slippers have a pancake with syrup and butter design on them. His eyelights are square shaped and the color of butter, along with syrup poured over his head with a slice of butter on top.
Routes: On the genocide route, Sans behaves as usual, observing Frisk from a far and making a few comments on how they aren't acting like a normal, non-criminal, human child, and then going completely radio silent when Papyrus dies. That is, of course, until 'human' Frisk enters the judgement hall, where his battle begins. Sans's battle plays as usual, with some design adjustments to his Gaster Blasters; the changes being syrup drizzled on their heads with a slice of butter on top, and instead of them shooting laser beams, they spew concentrated beams of maple syrup at Frisk's soul. If a beam hits their soul, then their movement speed is slowed from the natural stickiness of syrup; effect lasting for 2 heartbeats. If Frisk decides to eat Papyrus's consumable during this battle, then Sans will immediately TPK them using a wall of Gaster Blasters, and momentarily changing his death screen quote to: "Shouldn't have done that." Instead of 'Get dunked on.' After the battle is over and Sans wanders off screen to supposedly die, there would be an option to leave Papyrus's consumable on the floor of the hall to give Sans's nearby dish of pancakes company. A rare option for compassion during a genocide route.
On the pacifist route, Sans is your typical pun loving pile of pancakes (try saying that 5 times fast), who Frisk first meets after wandering out of the ruins. Sans introduces himself as "Sans, Sans the Skeleton, though I might be a pancake too," and then the rest of his regular dialogue follows. Sans annoys Papyrus and entertains Frisk and Grillby's bar costumers with skeleton puns, pancake puns, and skeleton pancake puns! Along with pranking Frisk by chugging a whole bottle of maple syrup in front of them. Though of course, when he's not found at Grillby's he will be out vending 'Sausage Cakes,' which look suspiciously like hot dogs, but if the bun were a full size pancake and the hot dog were a breakfast sausage.
Wrap up: There you have it for your syrup covered, pun loving, lazy boned skeleton! Here's a trivia fact: He has trouble seeing out of his left eyelight due to it being covered in maple syrup.
All colors pulled from this image:
(I pulled the color ref image from google, I do not own it)