My roomate has been trying to figure out the title of a game she remembers playing as a kid. Apparently it was played on a grid of some kind, and on each level there were different enemy characters (one level had swimming guys, another one had girls, etc.). You would move around on this grid flipping tiles, which would cause the whole row to flip (think domino effect) and push the enemies on screen into a wall, thus defeating them. The premise sounds insanely familiar to me, but I can't honestly think of anything that it could be.
She's also not entirely sure if it was for NES or SNES, but it was definitely on one of the early Nintendo consoles. Sorry the description is so vague, but any help would be greatly appreciated.