(I was reminded of the fact that there are people who honestly believe that if a speaker of British English had a moment of extreme emotion such as fear or anger, the affected British manner of speech would drop away and they would cry out in American English.)
But back to the evolution of language. Caesar makes only one other intelligible spoken utterance in the film. It is a full clause, well enunciated, right at the end. Naturally students of the evolution of syntax will want to know the structure. It is what The Cambridge Grammar of the English Language (CGEL) calls a complex-intransitive canonical clause, with copular be as its main verb.
Geoffrey Pullum of Language Log on Rise of the Planet of the Apes, the whole thing here.