Crush half of a graham cracker finely and set aside. Break the remaining graham crackers into coarse crumbs and place them in a mixing bowl.

To make the ganache, put the chocolate chips and 1 1/2 cups of the whipped topping into a microwave-safe bowl. Microwave on high for 45-60 seconds, stirring every 15 seconds, until the mixture is smooth and melted.

In a separate bowl, mix the pudding mix with the milk and whisk until it starts to thicken. Gently fold in the rest of the whipped topping.

Juice the lemon to get 2 tablespoons of juice. Peel the bananas and cut them into 1 1/2-inch pieces. Slice these pieces into a bowl and toss them with the lemon juice. Set aside 12 banana slices for garnish.

To assemble the trifle, start by spreading half of the crumbled graham crackers at the bottom of a trifle bowl. Layer half of the banana slices on top of the crackers, followed by one-third of the ganache. Spread half of the banana pudding mixture over the ganache, extending it to the edges.

Repeat these layers one more time. Finish by decorating the top with the remaining ganache and sprinkling the finely chopped graham cracker on top. Arrange the reserved banana slices around the edge of the trifle.