Thanks for the suggestions, everyone. I will check out Foster's and Totoro—they sound like great options.

I completely agree there's a lot for girls in Avatar, and the getting them both Avatar idea had occurred to me, but I was concerned that it might be too much for a 5-year-old. Or too talky, as you point out below.

So I'm looking for advice from my Avatar-loving comrades: I'm buying my 8-year-old nephew the first book of Avatar for Christmas, and I want a similarly awesome cartoon to buy for my 5-year-old, girly girl niece.  My first impulse was Powerpuff Girls, but I rewatched an episode online, and it seems more violent than I…