Ok You know when your playing your wii and u leave it for a sec it sort of says communications lost, well

Im playing SSBM On my wii and Im doing the 20 hr vs match thing,

will it do that communications lost thing or continue as if it was a gamecube?

whilst playing on a gamecube game the Wii remote goes into a sort of standby phase and it isnt connected to the game, the lost connection only happens in games where the pointer on the wiimote is being used. so in short u will be fine to do the 20hrs, thought it would be easier to stick 4 controllers and only do 5hrs. then just set it to one life so when the 5 hrs is over just kill the other guys.

I only have 3 conntrollers so here is what I did,

I had 3 hmn players, and 1 computer, I killed the 1 computer guy and left the 2 hmn and myself frozen taking the 2 out leaving my in...

when I wait a few hours will it still work or do I still need a computer in my game??

quote Mazda

so in short u will be fine to do the 20hrs, thought it would be easier to stick 4 controllers and only do 5hrs.

You can do that? I didn't think it mattered how many [human] players there were.

yep for every HMN player you have it reduces the time by 5hrs because the total time is still 20hrs of play.
nope you dont need a computer you just need to finish the game and not just quit.