After continuous resets and file manipulation the characters lost their memory. This affected everyone except Chara, Sans, Frisk and Flowey. Sans was aware of the resets therefore could remember everything. His brother, however, couldn't recall anything. Flowey agreed to help Sans look for a way to restore everyone's memories.
Memory is more quiet then the original Sans. He doesn't say as many puns and is a lot more serious in this timeline.
Sans wears a dark blue jacket with grey floof around the collar. The floof is split with half of it being a dark grey colour and the other half being a lighter grey. He has cloudy purple glasses (the ones that you can get from Gerson in the game) and a grey lab coat tied around his waist.
He did use to work with Alphys and the previous royal scientist, Gaster.