The Mouse That Roared   Turn the invasion of New York scene into a spectacle full of bit players and visual action.   Richard Bellamy, Cape Cod Academy, Osterville, Mass.   We used olio drops to indicate various locations which moved the action quickly as set changes were minimal.   Bonnie Poffenroth, Prairie High School, Vancouver, Wash.   We used multiple curtains which added a lot to the production.   Kriss Yeager, Western Reserve Local Schools, Berlin Center, Ohio   Buy the sound effects tape, and start thinking about the soldier costumes early.   Peter DeAngelis, Ross Corners Christian Academy, Owego, N.Y.