I don't think there's any question that your example in all its forms is criticism and fair use. Now, parody, for example, can be a more difficult beast. The estate of Margaret Mitchell did not take kindly to Alice Randall's "The Wind Done Gone" last year, calling it a derivative and infringing work, but an appellate court disagreed and said Ms. Randall's work was a not only a fair use but an appropriate exercise of her first amendment rights (more here). Justice Potter Stewart famously said of obscentity that it was difficult to define, but you know it when you see it. This kind of ad hoc approach creeps into the way the courts analyze copyright disputes as well, as they try to strike an appropriate balance and prevent the wholesale misappropriation of protected materials.
By the way, just what has become of the Klingon figure bloggers? Google has a Klingon interface, after all, and I do note it is impossible to make out the features of the pair on the IBU home page.