Considering Frankie looks like that a lot in the actual show, I think it's understandable that they drew her that way. I doubt it was originally drawn with the intention of making it into a shirt.
It's awesome though. NEEEEED.
Anyways, here's the actual picture from the blog, which I thankfully saved since now I can't find it anywhere on his blog:
Terrence is off to the side there, but maybe he isn't on the shirt. Darn.