Prepare the cake as directed on the back of the package. Allow to cool completely. Cover and allow to sit at room temperature overnight.
Prepare the frosting by melting the chocolate and coconut milk together in a small saucepan. Whisk until smooth. Transfer to a large bowl and refrigerate overnight.
The next day, remove the frosting from the refrigerator and allow to sit at room temperature for 15-20 minutes. Using a handheld or stand mixer with the paddle attachment, whip the frosting until fluffy and smooth.
Crumble all of the cake into the bowl on top of the frosting, making sure there aren't any large lumps. Using the mixer, beat the frosting and cake crumbles together until combined.
Scoop out 1 tablespoon of the mixture and roll into a ball. Place on lined baking dish or sheet and refrigerate for 30-minutes to an hour. Don't skip this step! It will help them hold together properly.
In a small saucepan, melt together the chocolate and coconut oil for the coating. Whisk until smooth. Transfer some of it to a 2-cup liquid measuring cup (which is ideal for dunking).
Remove a few cake balls from the refrigerator at a time. Dip a popsicle stick into the chocolate by ½-inch then insert it ¾ of the way into the cake ball. Dip the cake ball into the coating until it is completely covered in chocolate. Gently roll and tap the stick along the rim of the cup to allow excess coating to drip off. Top with sprinkles then poke into a block of styrofoam, a cardboard box or an upside down colander to dry. Repeat this step for remaining cake balls, removing a few at a time from the refrigerator. It's important to keep them cold prior to coating to make sure they hold together properly.
The cake pops should set up within an hour at room temperature. Refrigerate for up to 1 week or freeze (after fully set) for up to 6 weeks.