imgflip.com/i/a2ijlm link to the guessing game bruh-
also answers for it
First one is "Birdtale! Sans" from Birdtale
And Second one is "Bill Cipher! Sans" from the fandom, he doesn't have an exact AU
and the Third one is "Infected! Sans (also known as "Jacob" or "Conduit of DESTRUCTION")" from Alphatale