Well, just maybe you have seen some of his work before... even before it became his work. Yes, it seems that "post-pop artist" Todd Goldman (who also paints the images on his tees) may, just may have produced and sold images that were... let's think of a delicate way to explain this... already created by another artist. Yes, indeedy, and you thought plagiarism was limited to graduate school dissertations. You should read the entire list by Mike Tyndall, it's quite interesting. Very interesting.
And maybe you should buy a David and Goliath tee--it's kinda like lotto for the socially hip. You just don't know which artist your money will end up supporting.