"WiiSPACE is an original retro-themed spaceship shoot-'em-up supporting up to 4 simultaneous players for co-operative play. Features include powerups, bosses, high scores, and an aiming system allowing independent movement and targeting."
Or when your player dies, you can say in code, if enemy exists, do nothing, but if enemy does not exist, then create enemy at certain spot. (This would be a pain tho for lots of emeies)