31-in-1 is an unlicensed Famicom/NES multicart that was notably common in North America. It also "borrows" assets from the Famicom Disk System and music from Booby Kids of all places.
Unused Graphics#
There is Chinese text that reads "Xu Xinqi". Must be one of the developers.
Unused Text#
Starting at offset 0x81B39 in the ROM is several unused text strings referencing various games, including several which aren't on the cartridge.
PIECES CHESS
MAH JONG
PIN BALL
POPEYE
ZINJA
MAPPY
POOYAN
URBAN CHAMPION
Immediately after this is likely code created for an early version of the menu, with only the first two games referred to by name. (the first line was likely never meant to be displayed anywhere)
SUPER KIDS
SUPER KIDS
MARIO BROTHER
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31