For as long as Discord can remember, Fluttershy has always more or less feared Nightmare Night, even going so far as to barricade her self in her room and settle down for the night with her animal friends and comforting, sappy novel- which is dreadfully boring in his opinion. As for his own take of Nightmare night, well, simply put he finds it pathetic and cheesy at best. Not really his cup of tea. That all changed once his own spawn became old enough to join the parade of candy obsessed foals.
 
 
Since Fluttershy was busy hiding in her blanket fort with Lokie, it was up to Discord to supervise Harmony’s trek for treats. At first he was apathetic about the whole ‘dress up and go door to door asking for free stuff’ shabang, but once he saw how much Harmony was enjoying herself and how much fun he could have light-heartedly tormenting the residents of Ponyville without repercussions, he really got into the holiday spirit.
 
 
From then on, Discord and Harmony became something of a tricker treating sensation, always doing paired costumes. The wary adults were usually set on edge by Discord’s appearance and often shoved all the candy they hand into Harmony’s bag so that the beast would be satisfied and leave them alone. The foals on the other hand absolutely adored his frightening tales with scary monsters to boot, as well as other magical feats that were as enterianting as they were possibly illegal. But as much as Discord loved spreading harmless terror, it was bonding with his little Mo mo that truly made the holiday special. It was the special time for the just the two of them to gorge on sweets and insight a teensy bit of chaos.
 
Once Harmony grew up and started tricker treating on her own and going to parties or haunted houses with her friends, Discord continued to do his part in livening things up a bit. Even though Discord misses talking his squeaky four year old to trick for treats, he looks forward to the day when he can do it all over again with his future hybrid grandfoals.
 

 
Also, I’m not canonically suggesting that the TV show Gravity Falls exists in the KOPverse, I’m only implying is that if it did, Harmony would certainly relate with Mabel pines.;) (Wink)
 
a̶l̶s̶o̶ ̶D̶i̶s̶c̶o̶r̶d̶ ̶t̶e̶c̶h̶n̶i̶c̶a̶l̶l̶y̶ ̶f̶i̶t̶s̶ ̶t̶h̶e̶ ̶d̶e̶s̶c̶r̶i̶p̶t̶i̶o̶n̶ ̶o̶f̶ ̶a̶ ̶s̶u̶p̶e̶r̶n̶a̶t̶u̶r̶a̶l̶ ̶b̶e̶i̶n̶g̶ ̶f̶r̶o̶m̶ ̶a̶n̶ ̶a̶l̶t̶e̶r̶n̶a̶t̶e̶ ̶u̶n̶i̶v̶e̶r̶s̶e̶ ̶t̶h̶a̶t̶ ̶a̶t̶ ̶o̶n̶e̶ ̶p̶o̶i̶n̶t̶ ̶p̶l̶a̶n̶n̶e̶d̶ ̶t̶o̶ ̶m̶a̶k̶e̶ ̶r̶e̶a̶l̶i̶t̶y̶ ̶v̶e̶r̶y̶ ̶m̶u̶c̶h̶ ̶l̶i̶k̶e̶ ̶t̶h̶e̶ ̶o̶n̶e̶ ̶b̶a̶c̶k̶ ̶a̶t̶ ̶h̶i̶s̶ ̶h̶o̶m̶e̶.̶