1Heat oven to 350°F (325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups.
2In large bowl, beat cake mix, water, oil, eggs and 3/4 cup peanut butter with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Divide batter evenly among muffin cups (about two-thirds full).
3Bake 18 to 23 minutes or until toothpick inserted in center comes out clean. Remove from pan to cooling rack. Cool completely, about 30 minutes.
4In medium bowl, stir together frosting and 1/4 cup peanut butter. Frost cupcakes with frosting mixture. Sprinkle with peanuts; press lightly into frosting.