Furbies just have a simple microcontroller and the code has been released [1]. It's a clever bit of code to give the impression of intelligence, but it doesn't have anything like the abilities in urban legends. You could put other hardware in them of course, they'd be prime targets for that kind of thing.
OMG, it's 6502 code! (Or for some variant of the 6502.)
Marginally interesting, the source uses standard MOS assembler syntax, but Intel-like xxH notation for hex values, rather than $xx.
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[Edit] According to Wikipedia, actually a Sunplus SPC81A microcontroller using the 6502 instruction set, but lacking the Y register:
> The first Furby model was based around a 6502-style Sunplus SPC81A microcontroller, which had 80 KiB of ROM and 128 bytes of RAM. Its core differed from the original 6502 in the lack of the Y index register. The TSP50C04 chip from Texas Instruments, implementing the linear predictive coding codec, was used for voice synthesis.
it's certainly possible with a modified furby. there could have been a voice recorder placed inside, but that threat seems possible with other toys as well, maybe there was some opportunity due to the popularity of furbys.
in terms of the furby's unmodified hardware capabilities, the microphone was simply used for volume level reaction. reading through the furby's firmware, the mic was used as a peak volume input.
