Preheat the oven to the temperature on the back of the cake box. Prepare both cake mixes in separate bowls according to the box instructions. Place a Bundt pan on a sheet pan. Add about 2 scoops of the yellow cake batter into the pan, leaving space between them.
Add 2 scoops of chocolate cake batter into the spaces next to the yellow batter. Use a butter knife to lightly swirl the batters together. Avoid overmixing - you want a marbled look, not blended batter.
Repeat the layering and swirling process until the batter reaches about 2 inches from the top of the Bundt pan. Bake according to the times listed on the box instructions. If the center is still jiggly, bake a few extra minutes until it sets.
While the cake bakes, toast the coconut in a dry skillet over medium heat until golden brown. In a large bowl, beat the butter, powdered sugar, milk, and vanilla until creamy to make the icing.
Let the cake cool completely. Once cooled, spread the icing over the top. Press the toasted coconut onto the icing.
Warm the caramel slightly and add it to a ziplock bag. Snip the end and drizzle over the cake. Repeat with the melted hot fudge. Slice and serve.
