So I had the instructions and I did the quest for Vanya but I just got an item and I don't know how to use that item to turn my pet into nostalgic color. Vanya mentioned something about a Magic Bottle, but I don't what that means.

You need to bring Vanya an along with the toy he made for you.

thanks! also... ow! kind of expensive... gotta save up a little then

When you do get the essence, make sure you set the pet you want to change as your Active Pet. Vanya changes your Active pet. He doesn't ask who you want to change.

The essence of melody is given out as an achievement award for visiting Melody for the first 25 days of December. If you wait a couple months you can get one for free!

The user shop price is not really expensive at all sell lot of stuff and do quests and you will get the sp in no time