This is about Pokémon data that the game records during the course of the main storyline, which is then displayed during the credits. It stores the Encryption Constant (EC) followed by data which consists of their National Dex number, gender, form, and Shinyness.
Defeated Poochyena on Route 101:
0x1EAF8-0x1EAFB = Pokémon EC
0x1EAFC-0x1EAFE = Pokémon Data
Defeated Rival on Route 103:
0x1EB00-0x1EB03 = Pokémon EC
0x1EB04-0x1EB06 = Pokémon Data
0x1EB08-0x1EB0B = Rival's Pokémon EC
0x1EB0C-0x1EB0E = Rival's Pokémon Data
First Slot When Wally Caught Ralts:
0x1EB10-0x1EB13 = Pokémon EC
0x1EB14-0x1EB16 = Pokémon Data
Defeated Roxanne's Nosepass:
0x1EB20-0x1EB23 = Pokémon EC
0x1EB24-0x1EB26 = Pokémon Data
Defeated Brawly's Makuhita:
0x1EB28-0x1EB2B = Pokémon EC
0x1EB2C-0x1EB2E = Pokémon Data
First Slot When Met Steven In Granite Cave:
0x1EB30-0x1EB33 = Pokémon EC
0x1EB34-0x1EB36 = Pokémon Data
Defeated Wattson's Magneton:
0x1EB38-0x1EB3B = Pokémon EC
0x1EB3C-0x1EB3E = Pokémon Data
First Slot When Met Rival On Route 112:
0x1EB40-0x1EB43 = Pokémon EC
0x1EB44-0x1EB46 = Pokémon Data
Defeated Maxie's Camerupt/Archie's Sharpedo:
0x1EB48-0x1EB4B = Pokémon EC
0x1EB4C-0x1EB4E = Pokémon Data
Defeated Flannery's Torkoal:
0x1EB58-0x1EB5B = Pokémon EC
0x1EB5C-0x1EB5E = Pokémon Data
Defeated Norman's Slaking:
0x1EB60-0x1EB63 = Pokémon EC
0x1EB64-0x1EB66 = Pokémon Data
Defeated Winona's Altaria:
0x1EB78-0x1EB7B = Pokémon EC
0x1EB7C-0x1EB7E = Pokémon Data
First Slot When First Entered Team Magma/Aqua Hideout:
0x1EB80-0x1EB83 = Pokémon EC
0x1EB84-0x1EB86 = Pokémon Data
Pokémon No. 1 When Defeated Liza & Tate:
0x1EB88-0x1EB8B = Pokémon EC
0x1EB8C-0x1EB8E = Pokémon Data
Pokémon No. 2 When Defeated Liza & Tate:
0x1EB90-0x1EB93 = Pokémon EC
0x1EB94-0x1EB96 = Pokémon Data
Defeated Primal Groudon/Kyogre
0x1EBA0-0x1EBA3 = Pokémon EC
0x1EBA4-0x1EBA6 = Pokémon Data
Defeated Wallace's Milotic:
0x1EBB0-0x1EBB3 = Pokémon EC
0x1EBB4-0x1EBB6 = Pokémon Data
Defeated Wally's Gallade:
0x1EBB8-0x1EBBB = Pokémon EC
0x1EBBC-0x1EBBE = Pokémon Data
Defeated Steven's Metagross:
0x1EBC0-0x1EBC3 = Pokémon EC
0x1EBC4-0x1EBC6 = Pokémon Data
Some things to know:
-The Pokémon recorded during Wally's Ralts capture is not presented during the credits.
-Keep in mind that while the game can record battle-only forms such as Megas or Primal Reversions for non-battle scenarios, it's not legitimately possible. They also aren't recorded for Liza & Tate's battle.
-The Rival's starter has the following ECs as shown in a hex editor:
May's Treecko has 758F1C89
May's Torchic has D0362CCE
May's Mudkip has E652A959
Brendan's Treecko has 43361FC1
Brendan's Torchic has 56CA68C2
Brendan's Mudkip has 9ECCFBC8