Set out the number of parfait glasses you'd like to make for dessert. (It takes about a half slice for each glass.) Cut leftover pumpkin pie into small cubes or chunks. Be sure to break up the crust so there aren't any big, tough pieces.
Place whipped topping and pie chunks in repeated layers up the glass, evenly dividing the pie between the glasses. Finish with a dollop of whipped topping and sprinkle each glass with pecans. Enjoy!