New article of clothing

We were in Rosie's room, and she happened upon her Ariel doll, who was wearing her fins but had nothing on her top half.  Rosie frowned and said, "Uh-oh.  She needs her ninny-fitters."  Her daddy, who was more composed than I, said, "Oh, the seashells that fit on her ninnies?"  "Yeah, those ones."