In a medium bowl, stir together the cake mix, pudding mix, eggs, vegetable oil, and water until smooth. Add in the candy – reserving about 1/4 cup to sprinkle on the top. Spread the mixture evenly into the prepared dish and sprinkle the reserved candy over the top.
Bake about 25 minutes to until just barely golden brown. The mixture may seem jiggly or not completely set, but it will firm up as it cools.