I have done the quest and have the plushie but how do I make a Nostalgic Feli? I can't figure it out

You need both the plushie AND an Essence of Melody in order to make your Nostalgic pet.

Take the plushie and the item above to him. You can get the essence in December if you collect your daily Melody Cottage items from Dec 1-25, it's also a cash shop item, and user shops sell it.

I already bought the potion and i have the plushie but i don't know how to make the pet.

You go back to the toymaker and he should give you the option to make the pet once you finish the quest I believe?

Oh I forgot where he was I haven't been on in about a year. thank you everyone. I did it! I made Honey Bunches the adorable feli :3