Extracting Billy Hatcher “Joycarry Game” ROMs with Python

Billy Hatcher and the Giant Egg contains a feature called “Joycarry Games” similar to Animal Crossing’s NES game “Advance Play” feature. I wanted to extract the ROMs for these mini-games just like I did for Animal Crossing. Doing so wasn’t as straightforward; the ROMs aren’t available directly in the disc filesystem like they are in Animal Crossing. To extract the ROMs I ported an existing Rust program to Python (“rewrite-it-in-Python”, anyone?) that receives and saves the ROMs from the game running in Dolphin using the GBA TCP and Joyboot protocols.

These games are simple, and I only really played one as a kid: Puyo Pop. The game is similar to “Dr. Robotnik’s Mean Bean Machine”, which was a favorite of mine. This was the only way I could take that game “on-the-go”, often downloading the game to my GBA before road trips to see my grandparents.

Joycarry Game menu in Billy Hatcher with “ChuChu Rocket! Challenge” selected

The Python program is a port of this MIT licensed Rust program by Icedude907 with added functionality to save the EWRAM data after the ROM has been transmitted to the program via GBA TCP. I’ve distributed this program via a GitHub Gist.

Using the program requires the Dolphin emulator and dumping the ROM of the Billy Hatcher GameCube disc you intend to download Joyboot ROMs from. In the case of Billy Hatcher you also need to have unlocked the five different eggs hidden in levels. The fastest way to get around this is to download a 100% save file for your game’s region and place the file into Dolphin’s save file folder.

To extract the ROMs, launch Dolphin and set the controller in port 4 to be “GBA (TCP)”; Billy Hatcher in particular only works if the GC-to-GBA link cable is plugged into port 4. Start Dolphin playing Billy Hatcher, navigate to the world map, and then select “Joycarry Game”. From here you can select each game to be downloaded to our “GBA”, and the program should display information about receiving the ROM data.

Language setting and Joycarry ROMs

Something I did not know was that two of the five Joycarry ROMs, “ChuChu Rocket! Challenge” and “Puyo Pop”, have translations for both English and Japanese. Which Joyboot ROM translation is sent to you depends on the game region and which language is selected in the menu.

“ChuChu Rocket! Challenge”

“Puyo Pop”

The NTSC region (GEZE8P) of the game only supports English (no language selector in options) and only has English Joycarry ROMs. The NTSC-J region (GEGJ8P) supports Japanese and English, sending the corresponding Joycarry ROM depending on which language is selected. The PAL region (GEZP8P) supports English, French, German, Spanish, Italian, and ... Japanese! I checked each language, and the English Joycarry ROM is sent for all languages except Japanese.

Here are the SHA256 checksums of each ROM by game title and language:

Happy Halloween! 🎃👻

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