Seen June 26th, 2018
Posted June 18th, 2018
87 posts
5.4 Years
I'm not sure if this has been posted somewhere else, but...
To those people who want to expand the number of Pokémon on Emerald while retaining the animations:
Step 1:
You need to repoint the table that indexes all of the Pokémon front sprite animations. Open up a hex editor, go to 3299EC, copy 0x1B8 or 411 bytes of data into free space. You need to add as many 00s as there are new Pokémon after the end of the table. Repoint the table to your new location. There should be 4 pointers to repoint.

Step 2:
Next, you need to repoint the table that indexes all of the Pokémon back sprite animations. Go to 60A8C8, copy 0x1B8 bytes into free space, then add the 00s again. Repoint the table. There should only be one pointer at 17F488

Step 3:
Now, you need to repoint the table that controls the timing of the Pokémon frame switching. Go to 309AAC, select 0x6E0 bytes of data, and then copy into free space. Repoint it, there should be 5 pointers to the table. Now, how the table works is that it has pointers to certain strings of data that control the timing. Thus, we need to add pointers to the end to prevent glitches. The timing parameters that you should use vary between Pokémon and different versions of said Pokémon's sprite. For instance, Swalot's timing pointer is well-used for jumping frames and so on. Since there is no known index for the timing, the method I use is to observe different Pokémon animations in Emerald then choose from there. Also, when you repoint the normal palette table (the one at 0x303678), you have to index every palette properly. What I mean by this is that, for every entry of a Pokémon's palette:
70 6E C3 08 0B 00 00 00
You have to add 0x1 and write the bolded bytes in little endian form, as the front sprite animation routine uses this to determine which front sprite switching offset is to be used.
So for example, for Pokémon 0x1E9 (#489):
XX YY ZZ 08 E9 01 00 00
where ZZ YY XX is the offset where the palette is stored.
Credits to PurpleOrange for spotting the bug and Sky High for fixing it.

Step 4:
So, there is one final table we need to repoint. This table controls the amount of time that passes before the animation of the Pokémon is executed (thanks PurpleOrange). Go to 329B87, select 0x1B8 bytes of data (one for every Pokémon), then copy into free space. Now add as many 00s on the end as there are Pokémon. You can change this later to a higher number to delay the amount of time before the animation takes place. Repoint the table, there should be 2 pointers to it.

Step 5:
Finally, the limiters. In your hex editor, go to 0x34BFE and overwrite it with 07 E0 (for the sprites), and then go to 0xA5FEE and overwrite that with 03 E0. That's it!

For the front sprite and back sprite animations index, Chaos Rush has an excellent index here on Pokécommunity. Now the only issue will be the creation of 2-frame sprites for Gen IV to Gen VI. Personally, knowing that Flora Sky has sprites for Gen IV to Gen V, I think that if Sky were to let us use and resize his sprites we could come up with a pretty good repository soon. Another method would be to use the Sugimori palettes DS-style sprite repository that MrDollSteak has come up with, which covers Gen I to V.