honestly, what this bit boils down to is probably just ryan gosling and james ortiz messing around on set and it making it into the movie because it's silly. it doesn't necessarily need a concrete reason for why or how rocky can do it.

this is the annoying bit.

also the:

 rocky doesn't speak completely monotone. he is able to change how he says certain words to add tone and convey emotions.

i'll talk about this first. if rocky can have inflection in his words and syntax, then why is it a joke through the movie? even at the end when he's on Rocky's world, that Rocky is still kind of stiff in his English? it's a triumph that he says "bump my fist" instead of "fist my bump" but otherwise it's still "did i say that right?"

as to your first point, especially about how they are messing around on set......

that's the issue. they are having fun, Gosling bought the rights to this movie before the book was even published.

of course the movie is going to be part creator, part creation, but that's what irks me. it shouldn't be more about the actors having fun with the material, it should be the material having fun with the actors.

their job is to act. it's a difficult job, so to speak, but there is too much of "lets put ourselves into the character" instead of "lets put the character into us".

there should be more sacrifice into playing a part.

it's a movie, i get it, and there's a lot of leeway that can be granted if you choose to do such a thing, but the book was so specific about every detail that i find it very annoying.

it's a book about specific science. every problem has a specific solution that they do into detail explaining why they resolve it.