accompanying diaper bag. Do other dolls come with their own doll? Is this the right message to send children about overpopulation? Is it the right name for a doll? We guess we'll never know.
Right, you had a question. Yes, you can protect your doll under copyright law. You can file an application electronically or by using the Form CO (PDF). You would register it as a work of the visual arts. Circular 40 explain the rules.
Did the illustrator assign rights to you? According to your question, the illustrator created your doll. That might make the illustrator the copyright owner. If you and the illustrator jointly developed the doll, you may be co-authors. In any case, it's probably in your best interest to get an assignment of copyright from the illustrator. (This Artist's eGuide includes one).
What about trademarks? You can register your doll's name with the USPTO. But you don't get federal rights until you've started selling the doll (although you can reserve rights). If money is tight -- trademark registration costs approximately $300 -- you can wait until sales from the doll justify filing the application.