Our newer apps Toca Boo, Toca Nature and Toca Kitchen 2 are not supported on iPad 1 and iPhone 3GS. The reasoning behind this is that these apps require more support than the iPad 1 and iPhone 3GS can give. We've taken them though QA many times and they simply do not support the user experience we want to deliver. As never devices are becoming better and better, we need to prioritize and narrow down our support in order to deliver a product we're proud of.
There is a list of all supported devices per app in the App Store. If you can't find your device in the list it's unfortunately not supported.