On 1966’s Wonderfulness, Bill Cosby’s childhood memories fuel a slyly acerbic worldview. Kids are fun and magical, while their parents are con men and murderers. “The Playground” argues that grown-ups invented seesaws and monkey bars to kill off children. In “Chicken Heart,” moms and dads employ nefarious scare tactics to prevent toddlers from leaving their cribs. Cosby’s cadence has now entered its classic phase: slow and methodical, but ruptured by shrill voices and deep, guttural mumbles that look ahead to Fat Albert.