H.B.
We've done zoo animals (one a giraffe, the other a lion) and last year got matching chicken costumes from Old Navy - that was adorable! I thought about doing a chicken and an egg too, I think Parenting or Family Circle or one of those mags had a cute/easy pattern last year for a homemade hatching egg. For two little girls a butterfly and a flower would be cute, or maybe a flower and a bumblebee, I know I had a bumblebee costume for my son at 9 months, they are easy to find for babies. Have fun, I also love coordinating costumes - you're thinking ahead this year, I haven't even considered it yet!