Blanca is a mysterious cat whose face you can draw on.
How do I get Blanca in my town?
To get Blanca to show up in your town, use the phone in the attic of your house and say that you are OK with visits from the mysterious cat. Next, just connect to Nintendo WFC and open your gate. You don't need to have visitors come from other towns. After you close your gate, look around your town. You might find Blanca wandering around somewhere outside.
How do I draw a face?
When you agree to draw Blanca's face, it's just like drawing a pattern in the Able Sisters' store. Choose a color set at the bottom, choose a tool from the toolbar on the right, and draw in the center. Remember that if you choose a different color set, the colors in your current drawing will change to match the color set. You can't mix colors from different sets.
Who is Blanca the cat?
Nobody really knows. Blanca is a mysterious cat (THE mysterious cat, according to the phone in your attic) who might show up in your town after you connect to the Nintendo WFC. Blanca wears a dress, so she seems to be a girl, but maybe that's part of the disguise....
What's wrong with Blanca's face?
Blanca seems to want to hide her identity, so if you talk to her, she invites you to draw a new face for her. Before you do, you can take a look at her face to see what someone in some other town has drawn there. If you talk to Blanca, she'll tell you who it was who drew her current face, and what town she had her face drawn in.