Free homebrew arcade games for the Nintendo DS platform. This is also where many ports, remakes and homages to classic games that are not FPS or platform titles will end up. Shmups will typically be found here too.
I don't have a wii u anymore to test it myself, but if homebrews are not visible on the wii u menu I think you can press L + R + minus to open the plugin menu, there should be an option called "homebrews on wii u menu" or something similar
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)