Heat chocolate and butter in saucepan over low heat, stirring until melted and smooth; set aside.
Spread bottom of each cookie with 1 teaspoon of peanut butter; dip into melted chocolate mixture. Quickly press 2 pretzel twists on chocolate for frog legs with wide part of pretzels facing outward. Place pretzel-side down on waxed paper-lined baking sheet.
Attach candy pieces for eyes using remaining chocolate mixture or, if desired, additional peanut butter. Let stand until chocolate sets.