We had some Halloween-like stuff in World of Warcraft as well. During "Hallow's End", players could talk with innkeepers around the world, say "Trick or treat!" and either receive some weird gift or be transformed into something... odd. My favourite was the miniature Diablo that one innkeeper turned me into for a few seconds. The gifts were things like masks of the different races in the game, magic wands that could transform people into ghosts, pirates and more. Some gifts were of a slightly more useful nature, like food to replenish health and mana.

Although we don't have Halloween here (save for the continuing efforts of toy stores to make kids force their parents into buying costumes), Hallow's End was a fun little addition to the game.