1. Heat oven to 350 degrees F. Line the cups in two standard-size 12-cup muffin pans with paper liners.
2. Grate the zest from the orange (about 2 teaspoons). Squeeze juice from orange into a 1-cup measuring cup. Add water to measuring cup to equal 1 cup liquid; set aside.
3. In medium-size bowl with electric mixer, beat cream cheese, sugar, 1 egg and 1 teaspoon of the zest until smooth, about 1 minute; set aside.
4. In large bowl combine cake mix, 3 eggs, orange juicewater mixture, oil, remaining zest, cinnamon and chocolate syrup packet if included in box. With same beaters, beat on low speed for 30 seconds to moisten. Beat on medium speed for 2 minutes.
5. Fill each prepared muffin cup with scant 1/4 cup chocolate cake batter. Spoon cream cheese mixture into large pastry bag fitted with 1/4-inch plain round tip. Insert tip into batter of each cupcake. Squeeze some filling into center of each (top will slightly bulge).
6. Bake at 350 degrees F for 24 minutes or until toothpick inserted in center comes out clean. Remove cupcakes from pan to wire rack; let cool.While cupcakes are baking, make Frosting:
7. In large glass bowl, microwave chocolate chips on high 1 to 2 minutes, stirring to melt. With mixer on medium speed, beat in sour cream until fluffy and good spreading consistency. Let frosting sit at room temperature until cupcakes are cooled. Frost each cupcake with 1 tablespoon frosting. Store, covered, in refrigerator up to 3 days. Makes 24 cupcakes.