The only Halloween themed episode of an anime I've seen that I could think of is Bleach. It was actually nice to see a filler that wasn't boring because Bleach is notorious for having some of the worst fillers in the history of anime lol. @hikaymm
I'm a huge fan of themed episodes, especially holiday ones. It would be nice to see other anime get their very own Halloween specials because I gotta say the bleach one was hilarious.