If it's not in the books they can't do it. Between us and the rest of our family, we have over a dozen of these. The one we most want is Bernard from The Rescuers. Bianca is in the book so we have that, but for some reason as of our last trip no Bernard.
They are actually tracing most of the sketch, which is why it has to be in the book. After the trace the basics, they then go back on their own and finesse it to add the details.