Start by popping the popcorn kernels using your favorite method. Carefully sift through the popped popcorn to remove any unpopped kernels, and set the fluffy, popped popcorn aside in a large mixing bowl.

In a heavy-bottomed pot, melt the unsalted butter over medium-low heat, stirring occasionally to prevent browning. Once the butter is fully melted, add the miniature marshmallows to the pot. Stir frequently as the marshmallows melt, creating a smooth, velvety mixture.

Take the pot off the heat and pour the melted marshmallow mixture evenly over the prepared popcorn. Using a wooden spoon or spatula, gently toss the popcorn to ensure each piece is thoroughly coated.

Allow the mixture to cool slightly before incorporating the festive M&M candies and sprinkles. Use a rubber spatula to carefully fold them into the coated popcorn, taking care not to crush the candies.

To form the popcorn balls, generously coat your hands with non-stick cooking spray to prevent sticking. Scoop approximately one cup of the popcorn mixture into your hands and gently press it together to form a ball. Reapply the cooking spray to your hands as needed to maintain a smooth shaping process.

Place the finished popcorn balls on a parchment-lined baking sheet and leave them at room temperature until they are completely cool and firm. These cheerful treats are now ready to serve or wrap as festive gifts!