With one of my students, our "playing by ear and brain" activity has turned into a project to create her own set of simple variations on Twinkle, Twinkle Little Star. This is a great way to learn about variations as a compositional form and to teach some music appreciation and history. We listened to Mozart's Variations on "Ah vous dirai-je, maman" and used the worksheet below as a starting point.
Twinkle Twinkle Little Star
There are many good videos of this piece on YouTube, but I liked the view of the pianist's hands on this one.