I wonder how this lolcatz movement originated. The wikipedia article doesn't pin it down; just describes it as a parody of internet grammar (or rather the lack of it).
But I have seen something similar in Terry Pratchett's novels. For example, in Moving Pictures (1990) when a bunch of animals, who happen to be on the magical hills of 'Holy-Wood' suddenly start speaking English. The entire scene is gut-aching hillarious. And the cats speak exactly like these lolcatz!