Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
Add the cake mix, eggs, and oil to a large bowl. Stir until a thick, soft cookie dough forms.
If the dough is too soft to scoop or hold its shape, mix in 1 tablespoon all-purpose flour at a time, up to 2 tablespoons if needed.
Scoop tablespoon-sized portions of dough onto the prepared baking sheet, leaving about 2 inches between each cookie.
Bake for 7–9 minutes, or until the edges are set and the tops are lightly cracked. The centers should still look slightly soft.
Let the cookies cool on the baking sheet for about 5 minutes, then transfer them to a wire rack and cool completely.
Match cookies into pairs of similar size.
Pipe or spread vanilla frosting onto the flat side of one cookie, then top with a second cookie and press gently.
Tuck candy eyeballs into the frosting around the edges.
Serve immediately or store in an airtight container.