I knew the answer (that's my only Usagi shirt), but in doing additional research I typed "usagi yojimbo shirt" into my search bar. One of the first items to come up was a bootleg that used Travis Hanson's Usagi art that he did for the Sakai Project. At the time, the shirt had no reviews. I let Travis know that someone was stealing his art since only the IP owners are allowed to file a complaint with Amazon (I also tagged Stan's professional page in that post to let them know as well). Travis quickly let his fan base know about this art theft and less than 18 hours later the shirt now has 61 one-star reviews. I'd imagine it won't be up for much longer (hopefully Amazon takes the seller completely off, as they have a couple other Usagi shirts -one using Stan's art- and I'm sure they're not licensed).
So thanks for the trivia question. If it hadn't been for this particular question, that seller probably would have gone on selling bootlegs using Travis and Stan's stolen art.
I left my 1 star review on amazon.com right now. Thanks for helping spread the word so collectively we can act and have more influence. Great job, Kyle. Peace, maka