[ASM & Hex✓] How can I modify the first Pokémon encountered when rescuing Prof. Birch?

[Prcuvu]

Recently I started hacking GBA Sapphire ROM. When rescuing Prof. Birch at Route 101, the player encounters a Poochyena. I dug into the event and found that it is likely to be a part of a special event. Isn't it possible to modify this Pokémon?

 

[Aryan 10]

You better check out the script of Professor Birch's bag

 

[Prcuvu]

You better check out the script of Professor Birch's bag

I did so, it calls a special event 0x9C and then dialogues after the battle. Here's the script (I was using a Japanese ROM):

#org 0x14DB81
lock
faceplayer
setflag 0x800
setflag 0x52
fadescreen 0x1
hidesprite 0x4
movesprite 0xFF 0x6 0xD
applymovement MOVE_PLAYER 0x81803D9
waitmovement 0x0
special 0x9C
waitstate
applymovement 0x2 0x814DBD9
waitmovement 0x0
msgbox 0x814DC42 MSG_KEEPOPEN
special 0x0
setflag 0x2D0
clearflag 0x2D1
setflag 0x2BC
setvar 0x4084 0x2
setvar 0x4060 0x3
clearflag 0x4000
warp 0x1 0x4 0xFF 0x6 0x5
waitstate
release
end

The Pokémon's data is likely to be inside the special event 0x9C. Seems that this event consists of choosing starter and first battle vs Poochyena.

 

[DizzyEgg]

Recently I started hacking GBA Sapphire ROM. When rescuing Prof. Birch at Route 101, the player encounters a Poochyena. I dug into the event and found that it is likely to be a part of a special event. Isn't it possible to modify this Pokémon?

I don't know about Sapphire, but in Emerald:

Change byte at 08032706 to pokeID / 2. If you'd like a poke with an odd ID, then you'd have to change the code.
The instructions at 08032706 are:
mov r0, #0x90
lsl r0, r0, #1 //multiply 0x90 by two

Btw, the byte responsible for level is at 08032714.

 

[Prcuvu]

I don't know about Sapphire, but in Emerald:

Change byte at 08032706 to pokeID / 2. If you'd like a poke with an odd ID, then you'd have to change the code.
The instructions at 08032706 are:
mov r0, #0x90
lsl r0, r0, #1 //multiply 0x90 by two

Btw, the byte responsible for level is at 08032714.

Thank you very much. I've successfully located corresponding code in Sapphire and done my modification:
08008e54 218f mov r1, #0x8f
08008e56 0049 lsl r1, r1, #0x01
08008e58 9500 str r5, [sp, #0x0]
08008e5a 9501 str r5, [sp, #0x4]
08008e5c 9502 str r5, [sp, #0x8]
08008e5e 9503 str r5, [sp, #0xc]
08008e60 1c20 add r0, r4, #0x0
08008e62 2202 mov r2, #0x2
08008e64 2320 mov r3, #0x20
08008e66 f02e bl $08037ba4

 

[DizzyEgg]

Thank you very much. I've successfully located corresponding code in Sapphire and done my modification:
08008e54 218f mov r1, #0x8f
08008e56 0049 lsl r1, r1, #0x01
08008e58 9500 str r5, [sp, #0x0]
08008e5a 9501 str r5, [sp, #0x4]
08008e5c 9502 str r5, [sp, #0x8]
08008e5e 9503 str r5, [sp, #0xc]
08008e60 1c20 add r0, r4, #0x0
08008e62 2202 mov r2, #0x2
08008e64 2320 mov r3, #0x20
08008e66 f02e bl $08037ba4

Just one thing. Sapphire is (along with Leaf Green) the least supported rom out there. No research has been on that game, no resources, no patches, etc.
I'd suggest switching to Emerald(or Fire Red) as it has thousands of new features whereas Sapphire has nothing.