Luna Eclipsed

Luna Eclipsed is the fourth episode of the second season of My Little Pony Friendship is Magic, and the thirtieth episode overall.

Summary
It's Nightmare Night and the macabre celebrations are in full swing when Luna herself shows up in Ponyville, determined to change her frightening public image.

Verizon FiOS summary
As Nightmare Night falls, and the spooky celebrations are well under way and Luna herself makes a special appearance in Ponyville, causing many to be frightened, but she is determined to change her gruesome public image.

Trivia

 * The episode's title is a pun on the term lunar eclipse, an astronomical event that occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon, causing it to turn red.
 * A billboard referring to the Halloween episode has been put up in Los Angeles. In it, it shows Pinkie Pie with a Spike plushie in front of a TV screen, a parody of the poster for Poltergeist.