The Trick or Treat stamp is a stamp on Club Penguin Rewritten which has been released since the game begun, but could never actually be obtained.
This was due to a bug in the previous Halloween Party where it did not work, but the good news is that stu has confirmed it will be working during this year’s party:
Pinpin516: Will the trick or treat igloo stamp be fixed?
stu: During the Halloween Party, yes
Quite a bit has been revealed about October, and you can view all of that information here. Also, regarding the Fair, stu confirmed it is this month’s party and the bugs we saw last year won’t be present at this event.