so, i have this idea that i absolutely adore with the multiverse, one of the main things, is that in the classic universe, there has to be a sans, if there isn't then itll damage or distort the multiverse and cause more damage, so instead, whenever classic is required or wants to go to the multiverse, another sans takes his place.
this is underswap covering for classic, almost any sans is able to as long as they look similar enough to classic sans
the main things to look for is:
around the same height
same or similar bone color
enough mental stability
optional:
same magic color
same magic based abilities
same stats
the main ones excluded are, insanity sans, nightmare sans, error sans, death sans, geno sans (or any variant that cant exist in reality due to injuries)
they are excluded because of the fact they cant be hidden very well, and death could kill everyone which causes issues as everyone stems from the classics which, if damage is done will effect the rest of the multiverse
yes that means that they cant really do anything unless they absolutely have to if frisk ends up resetting, and they have to really bullshit their way through attacking the human and hoping it isn't obvious.
i know some may be out of character but its my version of them just like always so, enjoy :D (there is way more about my version of the multiverse but it'll be in random comics that i eventually show)