Do you have four ingredients? What? That's it? Gotta try it...
So here it is...slightly adapted:
Pumpkin Frozen Yogurt15 oz can pureed pumpkin
2 cups low fat vanilla yogurt
1 tablespoon sugar
1 teaspoon pumpkin pie spice
Add whatever toppings you like. Whipped cream makes it feel more pumpkin pie-y (if that's a word). Chopped nuts, chocolate chips, and pieces of pie crust would be other good toppings.