Hey i wanted to know what will happen if i download hacked stages or characters on my wii without the homebrew channel or ocarina program.

Will it mess up my wii in any kind of way?

you can download stages that were built in the stage studio and then put them in your sd card and play them
without having homebrew (or ocarina) the stage studio wont mess your wii (well it didn't in my wii)
i dont know if there are hacked characters,but if they exist i think they are going to mess something
hope it helped