Prepare cake batter as directed on package; stir in cookies. Spoon into 24 paper-lined muffin cups.
Bake 20 to 25 min. or until toothpick inserted in centers comes out clean. Cool cupcakes in pans 10 min.; remove to wire racks. Cool completely.
Beat pudding mix, milk and sugar in large bowl with whisk 2 min. Stir in COOL WHIP and food coloring; spoon into pastry bag fitted with round tip.
Pipe pudding mixture in zigzag pattern on tops of cupcakes to resemble brains, starting in center of each cupcake before filling in sides. Keep refrigerated.