This is my own pattern that fits 12″ Blythe dolls.
A sweet little all in one playsuit, perfect for lounging around the house in. Knit from the neck down all in one piece with a picot edge around the hem of the legs. I have embellished with a little crochet flower but you could add any pretty decoration of your choice.
I also have a free pattern for socks available that match this lovely.

You will need 2mm needles and very fine yarn (UK laceweight) some fine 2 ply yarns would work nice too.