Finely chop half of a graham cracker using a food chopper and set it aside.
Coarsely crumble the remaining graham crackers into a small mixing bowl.
For the ganache, place chocolate morsels and 1½ cups (375 mL) of the whipped topping into a small batter bowl, then microwave on HIGH for 45–60 seconds or until smooth, stirring every 15 seconds.
In a large mixing bowl, whisk together the pudding or pie filling and milk until the mixture begins to thicken.
Fold in the remaining whipped topping with a small scraper and set the mixture aside.
Juice a lemon using a juicer to measure 2 tablespoons (30 mL).
Peel the bananas, cut them into 1½-inch (4-cm) pieces with a paring knife, then slice them using an egg slicer into a medium mixing bowl.
Add the lemon juice and gently toss the bananas; reserve 12 slices for garnish.
To assemble, layer half of the crumbled graham crackers at the bottom of a trifle bowl, then layer half of the bananas, followed by one-third of the ganache.
Spread half of the banana filling evenly over the ganache.
Repeat the layers once more.
Decorate the top with the remaining ganache, sprinkle with the finely chopped graham cracker.
Arrange the reserved banana slices around the edge of the trifle.