Halloween Event 2019
The Halloween Event 2019 started the 27th of October and ended on the 6th of November.
Like most years you were able to get different Halloween Event Pokémons in exchange for Halloween Sweets. There were a total of 11 different Event Pokémons and one Legendary to obtain with 10 from previous years (Plaguekrow, Mega Crobat, Pumple, Zombeagle, Zomppet, Witch Vulpix, Sugar Shock, Dark Ponyta, Dralucha, Disguised Exeggcute and Nightmare Munna and Marshadow).
Besides this you were also able to buy yourself a Shiny or Normal Giratina Plushie in exchange for Halloween Sweets and also the Forme-change item Marshadium-Z, Misdreavus Cosplay and Griseous Pearl.
Halloween Sweets
Halloween sweets are obtainable through trick-or-treating a user, Rumbling, or through Interacting. The Halloween Sweets can be used to exchange them for items or Pokemon in the Halloween Store.
To increase the amount of Halloween Sweets you can purchase the Halloween Items in the Halloween Store.
Trick-or-treating
One of the possible ways to obtain Halloween Sweets is by Trick-or-treating a user. Similarly to the previous Halloween Event, there was a the Trick-or-Treat function added onto everyone's Userprofile. By trick-or-treating a user, you will obtain some Halloween Sweets. Each user can only be Trick-or-treated once a day.
Users had five options to get candies from Trick-or-Treating others just like last year:
Depending on what the user chose as what scared them the most, you got more candy based on what you dressed up as.
The higher your Skill Level is, the more users you can trick-or-treat daily and the more sweets you will get by trick-or-treating them. You can also trick-or-treat two more users per day if you purchased a 
"Creepy Doll".
Another way to increase the amount of Halloween Sweets you get is by purchasing the 
"Scary Glasses" item in the Halloween Store.
Interacting
Another possible method to obtain Halloween sweets was through Interacting. The amount of Halloween sweets you can get through interacting can be increased by purchasing the 
"Large Candy Bag" from the Halloween Store.
Rumbling
The last method to obtain Halloween Sweets is through Rumbling. Users are able to get a small amount of Halloween Sweets from rumbling when they retrieve their Pokemon. The amount of sweets obtained through rumbling can be increased when purchasing the 
"Explorer Halloween Upgrade" item from the Halloween Store.
Trick or Treat Skills
The Trick-or-Treat level determines how much Halloween Candy you can obtain when Trick-or-Treating a user. The level can be increased by interacting.