Heard about the Mega Drive cart "jiggling" or "Whipping out" and replacing with another game for some different effects, from infinite lives, level select etc. An old topic thread from the Sega 16 forums touches upon it:
http://www.sega-16.com/forum/archive/index.php/t-10588.htmlThere's a youtube video of Space Harrier 2 of the same method:
http://www.youtube.com/watch?v=cS2bMzoBjuMBut never heard of the N64 one, besides the abandoned Banjo and Tooie cart swap function, but if you can pull out the cart, why the hell not (besides the potential of killing your game)....