You will get 4 Chatterfang tokens and no Squirrel tokens.
As you resolve, Saw in Half, you observe its directions separately. Chatterfang is destroyed, and despatched to the graveyard. Then you’ll create 2 Chatterfang tokens, however Parallel Lives has a static potential that creates a alternative impact, changing the creating of two Chatterfang tokens with creating 4 Chatterfang tokens.
Although Chatterfang additionally has a alternative impact that might exchange making a token with creating the token and making a squirrel, there isn’t a Chatterfang on the battlefield on the time you’re making a token right here. The authentic one is within the graveyard and not one of the token ones have been created but. The new tokens will exist too late to do something right here:
614.4. Replacement results should exist earlier than the suitable occasion happens—they will’t “go back in time” and alter one thing that’s already occurred.