The Rubik's Cube wasn't originally meant to be a toy
"Although it is widely reported that the Cube was built as a teaching tool to help Ernő Rubik's students understand 3D objects, his actual purpose was solving the structural problem of moving the parts independently without the entire mechanism falling apart. He did not realize that he had created a puzzle until the first time he scrambled his new Cube and then tried to restore it."
http://www.buzzfeed.com/daves4/20-things-you-never-knew-about-popular-inventions