Apple of Enlightenment (ちえのリンゴ, Apple of Wisdom) is an item that predicts the future and is mentioned in Earthbound.
Giygas was in possession of the Apple of Enlightenment before the events of Earthbound, where it foretold Giygas's defeat at the hands of a child named Ness. To disprove this prophecy, he initiates his invasion of Earth 20 years before it was prophesied, only to be defeated by Ninten the first time.
The prophecy was still being told at least 10 years into Ness's future where he succeeded in plunging all into darkness, which prompts Buzz Buzz to travel back to Ness's time to warn him. Although it predicted that Ness and his friends would defeat Giygas, Pokey claimed that it never predicted his own involvement with Giygas' plans.
There is a theory that Apple Kid is the one who wrote the Apple of Enlightenment. This explains why Pokey was never mentioned in the prophecy, since the two never heard of each other.