Preheat your oven to 350°F (175°C). Prepare a greased 9x13 inch pan.

Combine the lemon cake mix, eggs, key lime juice, vegetable oil, and water in a mixing bowl and mix until smooth.

Pour the batter into the greased pan and bake for approximately 20 minutes, or until a toothpick comes out clean.

Allow the cake to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Whisk the pudding mix with 2 cups of milk for 2-3 minutes until thickened, then refrigerate for 5-10 minutes.

For a graham cracker crust, crush the graham crackers and mix with sugar, brown sugar, and melted butter. Press into the bottom of serving bowls if desired.

Once cooled, cut the cake into uneven pieces and begin layering in trifle bowls or cups.

Spoon a layer of pudding over the cake pieces, followed by a layer of Cool Whip.

Repeat the layering process until the dish is filled, ending with a layer of Cool Whip.

Garnish with optional decorations and serve immediately or refrigerate until serving.