Gently twist apart each Oreo so the cream filling stays on one half. I go slow here so the cookie doesn't crack in my hand. Set the plain cookie halves aside you'll sandwich them back on later.
Press four broken pretzel halves into the cream filling on each cookie, four to a side, so you end up with eight legs sticking out. I like to fan them out slightly so the spider looks like it's mid-crawl.
Microwave your chocolate chips in 20-second bursts, stirring in between, until fully smooth. I never rush this step overheating chocolate makes it seize up and turn grainy instead of glossy.
Dollop a small spoonful of melted chocolate onto the cream side, then gently press the plain cookie half on top. This chocolate layer acts as the glue that locks the pretzel legs firmly in place.
Spread a little more melted chocolate on top of each cookie, then sprinkle on your chocolate jimmies while it's still wet. I press two candy eyes on right after so they stick without sliding off.
Place your finished spiders on the parchment-lined baking sheet and let the chocolate firm up completely at room temperature, or pop the tray in the fridge for about 10 minutes to speed things along.
