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.
Revealing mistake: Just before Hermione gets struck in the chest by the branch of the Whomping Willow, if you play the scene in slow motion you will notice Hermione has padding underneath her pink jacket. (01:25:25)
Hamster
Suggested correction: Slow motion mistakes are not allowed under site's rules.
Sacha