This story is a sequel to The Perfect Little Village of Ponyville
After Vinyl Scratch helps Twilight to escape from the deadly dreams the Elements of Harmony have all been trapped in, they decide to head back to save the others, and to start with the dream world of Pinkie Pie, since she surely would be the best guide to get them through the dreams of anypony.
In retrospect, two ponies treading alone into the mind of the pony with Pinkamena in her head might have been a less than wise decision...
Sequel to "The Perfect Little Village of Ponyville" (which the above description just spoiled utterly if you haven't read it yet). Additional tags may be added after the story spoils them.