See 10 Trick-or-treat igloos at the Halloween Party
If you tried to open the Spy Phone in the Dark Swamp, it would display "NO SIGNAL" on the screen, and you were unable to teleport.
For a short time during the party, you were able to go out of bounds in the Dock, Forest, and Lighthouse. However, this was patched in the 220.127.116.11 update.
Numerous easter eggs were hidden throughout the island during the duration of the party. Most notably, an Evil Puffle could be seen at the top of the Pet Shop and a lanky figure, shrouded by trees, was in the Forest.