The Korok Ceremony is an annual event from The Wind Waker. Held in Forest Haven between the Koroks and the Great Deku Tree, it is a fun affair to celebrate their new year involving music, and ending with the Koroks flying out over the Great Sea to plant the Deku Tree's seeds.
To begin the ceremony, all the Koroks must gather around the Deku Tree to prepare for their long journey to somewhere in the sea. Makar then plays a special song on his violin, causing the Deku Tree to sprout seeds, which the other Koroks take to plant new forests.
The Wind Waker
When Link arrives at Forest Haven at the behest of the King of Red Lions, he is forced to remove an infestation of ChuChus from the Great Deku Tree. Once he has done so, the Deku Tree thanks him. Realising it means Ganon has returned, he promises Farore's Pearl to Link once the Korok's annual ceremony is complete, stressing the ceremony's importance, but then finds it cannot go ahead as Makar has disappeared into the Forbidden Woods. He asks Link to rescue Makar, and gives him a Deku Leaf to that end.
Once Makar is rescued, the Deku Tree lightly chastises him to be more careful, but reassures him that he need not cry, just play his song as part of the ceremony. After giving Link the Pearl in return for Makar's rescue, the ceremony begins - Makar plays his song, leading the Deku Tree to set seed, and the other Koroks to take them, promising to continue spreading new forests across the Great Sea.
Only two Koroks remain in Forest Haven afterwards - Makar to write the song needed for the next year's ceremony and Hollo to run his potion shop, Hollo's Forest Potion Shop.