FRLG on Switch uses a modified ROM, cannot be played on mGBA

[Flit]

FRLG just released on Switch.

The ROM is modified, for LeafGreen at least; its checksum doesn't appear on No-Intro and it crashes immediately in mGBA. I'm not sure what they could have done to cause it to crash. The copyright notice startup screen was at least modified to remove the white flash, but I doubt that alone would cause a crash in standard emulators...

EDIT: This is actually because the backup memory is missing / not emulated.

(For clarity, this won't affect playing normally on the Switch, it runs well there.)

[Flit]

Oh, saving is way faster than vanilla. I wouldn't be surprised if they changed the save structure too...

[Flit]

Hmm it does not crash in Bizhawk.

Also, if you want to dump saves, use Checkpoint. JKSV crashes for some reason

[Flit]

looks like the game was recompiled for the switch

the ROM header version is 0x0a
there's also a second build date with a git commit(?) hash
2025 12 19 15:38 22afedd9
there's also some kind of emulator hypercalls

my knowledge on poking around in this stuff is not amazing so i'm probably going to leave it here. either way, this rom is unlikely to work with emulators or real GBA hardware. a shame, but not a surprise

[Flit]

YOU GET THE TICKETS FROM OAK AFTER BEATING THE ELITE FOUR

[Flit]

capping off this thread by recapping what we know now (this is still developing but most of what we know is sorted now):

• the rom was recompiled to make minor changes, rather than using the 3ds vc approach of patches on runtime. it has a build date of December 19, 2025.
• the Switch's bad word filter is used for trainer and pokemon names.
• defeating the Elite Four for the first time will give you the MysticTicket and AuroraTicket!!
• the mail glitch is still present, and therefore ACE is possible; however, due to emulator differences and changes to script locations, ACE codes are different.
• the roamer bad IV bug is still present. however, the roamer roar bug was patched!
• you can still soft reset with A+B+Start+Select (and you can use X and Y instead of Start and Select respectively). this is the first pokemon game on Switch to let you do this.
• when using a Pro Controller or both Joy-Cons, enabling L=A will also remap the d-pad to act as the face buttons. this probably reflects the setting being called "One-Hand Mode" in the Japanese version.

i posted an earlier version of this list on the Bulbagarden forums here.