Just got an email from Justin at Weasel Farm. They’re pretty new, just formed in early 2008. Here’s the design philosophy from Justin himself,
The t-shirts almost always provide signature unique characters containing weaselly teeth and weaselly eyes. They provide a unique and interesting look while also providing some humor.
Right now they have two designs, with more on the way. I’d have to say my favorite is definitely Bull Shirt (the one on the left). Check them out at Weasel Farm. Also, the shirts are printed on American Apparel, if that’s a factor for you.