Mission 42: Collect hearts
Eliminate Heartless in this new world and collect hearts.
Roxas arrives at his new destination as Jack Skellington is still attempting to improve upon Halloween. Roxas also runs across the demented trio of Lock, Shock, and Barrel. Roxas's departure in turn inspires Jack's next Halloween spectacular!
Ah, at last, another new world. Halloween Town should, as usual, look extremely familiar to those who played the original Kingdom Hearts, down to the world layout. You'll enter the appropriately named Halloween Town Entrance and fight off some minor Heartless on your way to the Square. Upon arriving, more Heartless are hidden around the square, most notably near the entrance of the Graveyard, the southwestern corner, the northwestern corner, and on the stairs to Jack's House in the northern alcove.
Once you have found these Heartless, go into the Graveyard, where you will be greeted by five Hover Ghosts. Destroying three of them will fulfill the regular mission, while taking out all of them completes the optional goal as well. Whatever your choice, the ability to RTC will be opened, so take out as many as you like, and then head back to the Entrance to RTC. Mission complete!
Shouldn't be too hard if you have abilities equipped to help move around fast. Stock up on Fire to easily defeat Skater Bombs (as long as you are far enough away to avoid getting caught in the blast and getting frozen) and Hover Ghosts while using regular attacks against the Creepworms and just ignore the Shadows.