I found this tutorial and I really like this idea... depending on where you are in the world, I'd suggest mens shirts made from heavier fabrics (for those of us "up here" in Canada) such as corduroy, heavy twill, even polar fleece. Put a simple turtle neck underneath, and maybe some leggings.
I think I'm in love! (AGAIN!) This is a great idea. I actually did htis once for my daughter when she was 2. I used a womens button down dress. I can't wait to check out this tutorial. Thanks for sharing!