Reese's Pieces Peanut Butter Cups is the latest invention from the creative geniuses at Reese's. All along it was there right in front of us. Reese's Pieces combined with Reese's Peanut Butter Cups. Two of the most iconic brands combined together creating an explosion of sweet-and salty peanut butter goodness! Epic. Try Reese's Pieces Peanut Butter Cups King Size.