In a mixing bowl, combine peanut butter, granulated sugar, and brown sugar until smooth. Beat in egg and vanilla extract. Gradually mix in flour and baking soda. Refrigerate dough for about 30 minutes.

Preheat oven to 350°F (175°C). Line baking sheets with parchment paper. Scoop tablespoon-sized portions of dough, shape into balls, and place on sheets. Use a fork to create crisscross patterns. Bake for 10-12 minutes until golden.

Melt dark chocolate in a microwave-safe bowl in intervals, stirring until smooth. Allow to cool slightly before use.

Drizzle melted chocolate over cookies to create spider legs. Add chocolate sprinkles while chocolate is still gooey.

Before chocolate sets, gently press candy eyes into the top of each cookie. Allow cookies to sit for 30 minutes to set.

Transfer cookies to a platter for serving or store in an airtight container for up to 5 days.