Cut off tops of oranges. Gently hollow out pulp (reserve for another use), leaving a thick shell; hollow out pulp off tops also. Cut Jack-O-Lantern faces into each orange. Pack chocolate ice cream into shells, avoid letting ice cream come out of holes. Cut a hole into top of orange top. Set tops back on, over ice cream, and inset cinnamon stick stem through the hole. Place in freezer for at least 3 hours, or until serving time.