Ravelry: American Girl Doll Cosy Onesie or Snuggly Snow Suit Set (for 18" Doll & for Bitty Baby/ Using a Modification on the legs) by Jacqueline Gibb (Instructions for a: One Piece Suit, Hat & Mitens...with the addition of the earflap hat & mittens it converts from a fashionable "onesie" to a snow suit. )

17 Cosy Sleepsuit or Snuggly Snow Suit Set pattern by Jacqueline Gibb