Preheat oven to 325°F and lightly grease an 8 x 8-inch pan, or line with parchment paper.
In a medium bowl, whisk together eggs, melted butter (or oil) and vanilla extract. Add blondie mix and stir until fully combined.
Choose one variation. For Confetti, fold in sprinkles. For Fruit-Fetti, fold in freeze-dried fruit and chopped pistachios.
Spread batter evenly in the prepared pan. If using sprinkles, scatter more on top before baking.
Bake for 32–37 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Allow the blondies to cool completely in the pan before slicing.
If making the Fruit-Fetti version, whisk powdered sugar with milk or water until pourable.
Drizzle over cooled blondies and sprinkle with additional pistachios and crushed fruit. Let the icing set before slicing.
If using natural jimmy-style sprinkles, freezing them before baking helps maintain their shape and reduces color bleeding in the oven.