Yesterday I got this big envelop from Google, wondering what it was, I opened it up. It was an AdSense check, I thought maybe it was for the AdSense referral program because I never got a check from Google's AdSense program in that format. But I was wrong, Google simply changed their check format. Jensense reports that there is a New look for AdSense checks. In addition, there is forum chatter at WebmasterWorld.
And here is a picture for you: