By animal mode I mean start making noises liken that of an animal, usually without being prompted (or cause) but he is also very willing to cooperate encore demands.
His current best impression by far is that of our dachshund's cries (from being left home alone). In fact his whines are so much like Bob that once I had to ask my mum who was crying! (It was R).
His other favorite voices include elephant, chimpanzee and cat. He also does a mean impersonation of a crying baby (figures).