Crumble the cake and mix with frosting until it forms a ball and press it into a plastic wrap-lined 1 ½ quart bowl, cover, and refrigerate for an hour.
Meanwhile, heat the heavy whipping cream over medium heat until it just begins to bubble.
Pour it over the chocolate and let it rest for 3-4 minutes, then stir until creamy and smooth.
Set the ganache aside for about an hour until it thickens.
Remove the cake from the bowl and set the flat side on a cake board or large serving platter.
Spread ganache over the giant cake ball.
Press a spatula on the ganache then lift it off making spikes of fur all over the cake.
Cut out modeling chocolate eyes at press onto cake.
Pipe a thick layer of melted candy melts into eight angled 6 ¾" by 4 ½" spider legs. Chill for 10 minutes.
Frost the legs with ganache and make them look furry.