Speak with the innkeepers of Orgrimmar, Undercity, and Thunder Bluff, as well as Kali Remik in Sen'jin Village. Perform the tricks they ask of you in exchange for the treats they offer. Return to Spoops at the Orgrimmar Orphanage with a Thunder Bluff Marzipan, Darkspear Gumdrop, Orgrimmar Nougat, and Undercity Mint.
I want to go trick-or-treating, but I can't because I'm sick. If you go for me, I'd trade you the candy you get for some I already have! I think you'd like this candy - it makes you turn into things both funny and scary!
Each of the innkeepers in the big cities have candy they give for Hallow's End - talk to them and do the tricks they ask for! Also, a troll named Kali Remik in Sen'jin Village is handing out candy as well. When you have all the candy, bring them back to me here!