Preheat oven to 350 degrees F (180 degrees C). Grease a large baking sheet.
Cook popcorn according to package directions. Toss popcorn with marshmallows and chocolate chips. Spread out on the baking sheet and evenly sprinkle with salt. Make in preheated oven for 7-10 minutes or until marshmallows and chocolate are soft.
While the popcorn is baking, add the peanut butter to a microwave safe bowl. Microwave on high for 1:30-2 minutes, stirring every 30 seconds, until the peanut butter is thin enough to pour.
Remove the popcorn from the oven and pour peanut butter over it, distributing evenly.