Sirius Black: Brilliant, Snape. Once again you've put your keen and penetrating mind to the task and as usual come to the wrong conclusion.
Harry never notices that the name "Peter Pettigrew" appears on the Marauder's Map, right next to "Ronald Weasley." Way beyond a character mistake, as there's no way that wouldn't be cause for interest. If nothing else, Ron's brothers who had the map for years before giving it to Harry, would most certainly have wondered why their brother was sleeping with a person named Peter Pettigrew.
In order to acquaint himself with his three lead actors, director Alfonso Cuaron had each of them write an essay about their characters, from a first-person point of view. Emma Watson, in true Hermione fashion, went a little overboard and wrote an 16-page essay, Daniel Radcliffe wrote a simple one page paper, and Rupert Grint never even turned his in, as he said that is what Ron would have done.