Yarr Cute Mob Models Mod 1.8, 1.7.10, 1.7.2 replaces generic minecraft models with the designs used in mobtalker mod. It's mostly just a visual change, though some options allow to change the mob's model to match its hitbox, as well as a few other small things like removing the blaze's smoke or blaze rods.

edit: ability to change mob hitboxes is currently disabled due to crashing and compatibility problems. it might be restored sometime between now and next century when i figure out how to do that without changing the base code.