When Harry becomes the DADA professor, kids constantly ask him for an autograph, but he refuses, saying the only thing he’ll autograph is a detention slip. Eventually, though, he starts carrying around a stack of autographed pictures of Ginny, which he gives out when people ask for an autograph. It gets really popular, so he starts mixing it up with autographs from other people, mostly Ron and Hermione. But the students love it, so he adds more. Soon he’s giving out autographs from like fifty different people, including all the teachers at Hogwarts, and a bunch of other random people like Luna, Lee Jordan, Oliver Wood, etc. He even has some fairly rare ones from Krum and Fleur. It becomes a game in Hogwarts to collect all the autographs, like chocolate frog cards. Some of them are more limited edition than others, like signatures from all the ghosts (though Harry won’t reveal how he managed to get those). George starts to offer a discount at Weasleys’ Wizard Wheezes (and a prize autograph from Peeves, who will only sign Bertie Bott’s scratch-and-sniff cards) to anyone who can prove they’ve collected the whole set. Harry provides him with up-to-date lists of autographs to check against. Every Hogsmeade weekend there’s a line of Hogwarts students in WWW’s Hogsmeade branch trying to get the discount.
At some point a seventh year comes up to Harry and asks for his autograph, but not as the Savior of the Wizarding World, but because they now have the autograph of every other Hogwarts teacher and want Professor Potter’s to go with them. Harry–trying not to tear up–agrees, but only in exchange for the student’s signature. He begins offering this deal to all departing seventh years, his autograph in exchange for theirs. He tells them it’s in case they ever get famous, so he can add it as a limited edition autograph, but really he keeps them all in a big binder just for himself, to remember all his students. (A couple times, though, when a students does become famous, he will contact them and ask if they’d like to be added to the game. So far no one has said no.)
