First, make your Oreo balls. In a large food processor, grind the entire package of Oreos into crumbs. Add in the softened cream cheese in chunks and process again until fully moistened and combined.
Using a Tablespoon-size cookie dough scoop, portion out small round balls of the Oreo mixture, rolling them in your hands so they're as perfectly round as possible. Place on a foil-lined baking sheet and freeze until slightly firmed, about 15 minutes.
For the Oreo pumpkins: melt the orange candy melts according to package instructions or until smooth. Drop one Oreo ball into the melted orange chocolate and toss to coat with a fork. Gently lift the coated Oreo ball out and tap off excess. Slide it onto another foil-lined baking sheet (sometimes pushing it off the fork is easier with a toothpick). Immediately put a small 1/2" piece of a pretzel stick into the top while coating is still wet and sprinkle with orange sanding sugar. Let coating set, then decorate "leaves" with green gel.
For the Oreo bats: melt the chocolate candy coating according to package instructions or until smooth. Drop one Oreo ball into the melted chocolate and toss to coat with a fork. Gently lift the coated Oreo ball out and tap off excess. Slide it onto a foil-lined baking sheet. Immediately press two halves of an Oreo thin cookie into the sides of the ball for the wings. Working quickly, add two small eyeball sprinkles to the front of the ball and add two mini chocolate chips to the top of the Oreo ball for ears. Let coating set.
For the Oreo eyeballs: melt the white candy coating according to package instructions or until smooth. Drop one Oreo ball into the melted white chocolate and toss to coat with a fork. Gently lift the coated Oreo ball out and tap off excess. Slide it onto a foil-lined baking sheet. Immediately press a large eyeball sprinkle on the top of the Oreo ball. Let coating dry, then pipe on red squiggly "blood vessels" using a red gel writer. Let gel set, about 10 minutes, before serving.
For the Oreo mummies: melt the white candy coating according to package instructions or until smooth. Drop one Oreo ball into the melted white chocolate and toss to coat with a fork. Gently lift the coated Oreo ball out and tap off excess. Slide it onto a foil-lined baking sheet. Let Oreo truffles set, about 3 minutes. Spoon the rest of the melted white chocolate into a piping bag or a sandwich Ziploc and snip off the tip. Drizzle the remaining white chocolate evenly over the balls for the mummy "bandages." Immediately garnish with two bloody eyeball sprinkles on the front of the Oreo ball. Let set.