In a small bowl, beat the cream cheese, milk, garlic powder and onion powder until smooth; set side 1/4 cup. Spread 1 tablespoon of the remaining cream cheese mixture over each slice of bread. Top each with a cheese slice. Cut out each sandwich with a butterfly-shaped cookie cutter.
Cut 12 olives in half lengthwise; place two halves, cut side down, in the center of each sandwich for butterfly body. Cut remaining whole olives into slices; place two on each wing. Set olive ends aside.
Cut a small hole in the corner of a pastry or plastic bag; insert a small start tip. Fill bag with reserved cream cheese mixture. Pipe star on each olive slice; pipe two stars on front of each butterfly body for eyes. Cut olive ends into small pieces; place on eyes.