Plot hole: 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.
Suggested correction: JK Rowling explained why Ron's brothers didn't wonder why Ron was sleeping with a man named Peter Pettigrew. Here is the link: https://scifi.stackexchange.com/questions/11447/why-couldnt-harry-or-anybody-else-see-peter-pettigrew-aka-scabbers-on-the-marau.
jon snow