It's my take on error 404.
The player tired to delete him, but something came wrong.
Don't have a face, Windows 'ERROR 404 FILE NOT FOUND' window covers his face, but still can see.
Unlike original sans, he is more worried, depressed, gloomy, sad and anxious, but he has not lost his sense of humor.
Don't know Chara, but know the player and scare of him.
He weaker than original sans.
He don't know about AUs, but know that they exist.
His body shaking weakly or hardly, but not because of fear.