Club Penguin: Elite Penguin Force had the ability to download free DLC which is saved to the cartridge's save file, seemingly in the same ARC format used elsewhere in the game.
Sample, containing two pieces of downloaded DLC: https://github.com/wertercatt/Reverse-E ... LPPv00.sav
I've tried manually extracting the ARC using a hex editor, but I was unable to properly extract the entire file.
BMS definition for the ARC format used by this game, created by aluigi:
get FILES long
for i = 0 < FILES
get NAME_CRC long
get OFFSET long
get SIZE long
clog "" OFFSET SIZE SIZE