Why did Harry Potter look for Peter Pettigrew when he saw his name on the Marauder's Map in the third Harry Potter film? He could have just assumed that Peter Pettigrew was a ghost like the other Hogwarts ghosts.
1 Answer
Because Harry is curious.
He's been told that Peter Pettigrew is dead, he's never seen him on the map before and no-one has ever mentioned him.
Further more, he's associated the name 'Pettigrew' with 'Sirius' and his parents and he really wants to know the truth.