This homebrew application allows two (or more) players to play a Wii game's offline multiplayer over the network (online). This has been confirmed working for New Super Mario Bros. Wii and Wii Sports so far. Bugs and desyncs might still occur as of now.
Source code:
https://github.com/MrBean35000vr/netslug-wii
Enjoy
Source code:
https://github.com/MrBean35000vr/netslug-wii
Enjoy