Hey,
A few weeks ago I was playing Bubble Bobble with a friend and at some point I stepped on the joypad wire and the console moved. Not sure if this happened because of the joypad connector or the cart that moved... but this is what showed up:
It was stuck like that, buttons didn't work and I had to reboot. Really sorry about the extra blurriness, but I was not sober and thought the pic was taken correctly.
Above the Taito logo were some random letters and numbers, like a debug code or something like that. Google didn't help me so maybe someone here knows?