MELT 2 Tbsp. of the butter; place in medium bowl. Add crushed cookies; mix well. Remove 2 Tbsp. of the crumb mixture; set aside for later use.
PRESS remaining crumb mixture firmly onto bottom and up side of 9-inch pie plate; set aside.
MICROWAVE chocolate and remaining 2 Tbsp. butter in microwaveable bowl on MEDIUM 1 min.; stir until chocolate is completely melted. Spread evenly onto bottom of crust; set aside.
PREPARE dry pudding mix with 1-1/2 cups milk as directed on package. Top chocolate with bananas; pour pudding evenly over bananas. Refrigerate at least 4 hours or up to 24 hours. Top with whipped topping just before serving; sprinkle with reserved 2 Tbsp. crumb mixture. Store leftover pie in refrigerator.