Both WSJ and NYT have a story each Barbie and fierce rival Bratz’s online-mixed-with-offline social networking efforts, and interesting approaches for both. Mattel Inc.‘s Barbie launched its online social networks for kids, BarbieGirls, two months ago and three million of them have registered since then. Now MGA Entertainment-owned Bratz wil launch its social network on August 1.

Both have an offline component: The Be-Bratz site is accessible only after purchase of a special $29.99 Bratz doll that comes with a USB key, and then users will be able to choose a screen name and their own Bratz “avatar,” an online doll that can be dressed and tailored to their tastes. For Barbie, users don’t require to buy anything to join, but for special features, it is necessary to buy a $60 MP3 device that plugs into the computer via a USB port to get access to a “Club Beauty” where the avatars can get makeovers; a pet-adoption feature; and the ability to use a greater range of hairstyles, facial expressions, skin tones and fashions.

The MP3 player is central to a key mission for Mattel—winning interest from older girls who have drifted away from Barbie in recent years in favor of gadgets, the WSJ story says. The new doll is a roundabout way of charging for online content, says NYT.