In a medium (microwave-safe) bowl melt dark chocolate in 20-second increments in the microwave until fully melted. Stir in between melting to ensure the chocolate does not burn.
Using a fork, dip a pretzel stick in the chocolate and allow the excess chocolate to drip back into the bowl.
Place the pretzels on the prepared baking sheet and repeat with the remaining pretzels.
Chill the pretzels in the refrigerator for about 30 minutes or until set.
When the pretzels have set. Cut 3 of the sticks in half to form 6 legs.
Carefully separate an Oreo in half (gently twisting the cookie shells helps to loosen it). Place the cookie halves cream side up on the baking sheet. Smooth the cream with a butter knife or offset spatula if necessary.
Press 3 pretzel legs (cut side)into the cream on one side of a cookie half. Press 3 more legs into the opposite side of the cookie half.
Reassemble the cookie by topping the base with the other half of the cookie. Press gently to evenly distribute the cream.
Using some melted chocolate and a toothpick or cocktail stick, attach the candy eyes.
Add a red Jimmie sprinkle to create a mouth in the cream under the top cookie. Add some white Jimmies for teeth.
Continue until all spiders are assembled. Allow to fully set before enjoying.
Notes
Make sure that you use Double Stuf Oreos.
Other chocolates can be used, see some of my suggestions above.
Use assorted sizes of candy eyes.
Make sure that you chill the pretzels for at least 30 minutes.