An example of a highly confusing "science toy" (found in the gift store of the otherwise recommendable Australian Reptile Park): The "Kangaroo Egg"!
Children are instructed to put the kangaroo egg into a glass of water to watch a "pet kangaroo" hatch within 48h. Ironically, the emerging kangaroo carries a joey (baby kangaroo) in its pouch. How confusing is that! There is no explanatory text on the box that would clarify that kangaroos are marsupials that do not lay eggs.