Glass marble (the kind you put in fish tanks. Make sure one side is flat)
Glue (any kind, as long as it dries clear)
Print out a Harry Potter picture you like, making sure it is small enough to fit at the back of the marble.
Cut out that picture in a round shape and glue it to the back of the marble
Cut out the scrap piece of felt in a round shape and make a loop with the wire
Glue the felt to the back of the marble, making sure the pin is between the two
Add the keychain to the wire loop.
Tab's tutorial was taken with permission.