In medium bowl whisk together milk and 2 cups whipped topping. Add vanilla pudding mix. Whisk until mixture thickens to consistency of stiffly beaten whipped cream, about 1 minute. Stir in banana slices. Spread half of banana pudding mixture in pie crust.
Stir together fudge sauce and rum, set aside 3 TBS for drizzling. With back of spoon gently spread 1/2 remaining fudge rum sauce over banana pudding mixture. Top with remaining banana pudding mixture and other half of fudge rum sauce. Refrigerate until firm, about 1 hr.
Arrange pineapple chunks in single layer over fudge rum sauce. Spread with remaining whipped topping, filling spaces between pineapple chunks, and swirling topping into peaks with back of spoon. Refrigerate 30 minutes.
In microwave safe container, heat reserved fudge rum sauce on high until pourable, about 10 seconds. With fork drizzle sauce in lines over top of pie. Garnish with maraschino cherries and walnuts.