Line and grease an 8x8-inch baking pan.

Place all of the vanilla frosting and peanut butter into a microwave-safe bowl. Microwave for 1 minute and stir together until completely combined. Fold in 2 cups of popped popcorn.

Scrape the entire mixture into the prepared pan. Crumble up the remaining 1/4 cup popcorn and sprinkle it on top. Refrigerate for 2 hours, or until firm. Cut into 16 pieces. Enjoy!