Melt butter in a large saucepan over low heat. Add marshmallows and stir until completely melted. Stir in vanilla extract.

Pour the marshmallow mixture over the popcorn in a large bowl. Stir until all the popcorn is evenly coated.

Grease your hands lightly with butter or oil and quickly shape the popcorn into balls before it cools.

Decorate by adding sprinkles or festive candies while the popcorn balls are still warm.

Let the popcorn balls cool and set for 15 minutes before serving or wrapping them for gifting.