You’ll need this form, the UPC from the DVD package and the sales receipt date between 9/1/11 & 2/28/12.
Scooby-Doo! Legend of the Phantosaur is on sale for $9.99 at Amazon right now (50% off). I don’t see any reason why your receipt from Amazon wouldn’t be accepted for the rebate. So purchase it for half off at Amazon and get another $3.00 back!