Third Year and Fourth Year Changes
Harry and Percy can be a little closer than canon. Spades where this could happen are mostly in the third book. The scene where Fred and George joke about trying to lock Percy in a tomb could be triggering for Harry, who was locked in a cupboard as a punishment, which also needlessly served as his bedroom. Harry could go off on his own quietly and run into Percy,asking him if he was okay. Percy could reassure him, but also be a bit concerned by the reaction. Harry can also decide not to sneak into Hogsmeade. Instead, Percy can make a point to look after Harry and later Neville, hanging out with them. They find themselves having fun. However, Fred and George can still decide to give Harry the Marauder’s map, but because he saved Ginny the year before (I saw this in another fanfic, can’t remember the name, but Harry ended up finding a Crumple-Horned Snorkack and married to Luna) and because they felt bad about him having to hang out with Percy. Instead of going to Hogsmeade, Harry uses the map to get to explore Hogwarts and later investigate wormtail when his name shows up on the map. Lastly, Harry can tell Percy about Scabbers being Peter Pettigrew, which will be heartbreaking for Percy. During the summer before their fourth year, Harry and Percy have a few conversations as well after he is picked up. Percy can also check on Harry after his name comes out of the Goblet of Fire.
During fourth year, Harry skips the Yule Ball, not knowing that he was required to go (I’m going with the movie story line where they forgot to tell him). Maybe Harry can go to London instead. When Harry comes back, he comes home to Hermione and Ron feuding after the dance, and some of the other students not wanting to deal with them without Harry.
Since Harry doesn’t plan on going to the ball, he doesn’t ask out Cho, but he does talk to her and finds out that she’s going to the Ball with Cedric.