I have created stickers to use as tangible badges for your students to collect as they use Khan Academy. The stickers are printed on Avery 6450 labels and include moon, earth, and sun badges.
I was inspired to create these by Julianne Russell, who has shared how she used them in her classroom here:
Khan Academy Blog
I take no credit for the idea or the art provided by Khan Academy. I created this to help other teachers implement the same great idea that has been shared by Khan Academy.