Name: sans

his nickname would most likely be puns 

sans attacked frisk after his brother(just like undertale) had been killed but instead of getting his head cut off, frisk hung him, i will explain how in chara's part since she was the master mind behind it

his ecto color as you might tell is green

his skull is broken because of the fight and most of his other bones are too

his hands are black(not racist >:0) because gaster had cut off his arms before, so after feeling bad, gaster gives him new hands, but not the same color to remind sans that his old man got rid of his hands so ya he had a nice childhood