The goal of this topic is to inform people how to unlock as much as possible in as little time as possible. I had another topic on this, but I used the rather unreliable cheats and secrets section to compile it. This time, I used brawl central's info. For those curious, yes, this is DEFINITELY the fastest way to get the full cast and stage list. I can't say it's the most fun, but efficiency is our goal here. However, if things can be gotten without costing any time, provisions will be made to get them.
Start off by going into vs mode and setting it to Stamina Flower. Give the AI 1 HP and yourself more than 1 HP. Pick Donkey Kong and play on Shadow Moses Island for 15 matches. After five matches, you'll unlock Ness, after ten you'll unlock Marth, and after fifteen you'll unlock Snake and the Snake Eater Instrumental track. Switch the stage to Yoshi's Island (melee) and play 5 more matches. After three more, you'll unlock the Super Mario World demo, and after five more you'll unlock 75m (DK arcade). 20 matches total.
Now switch your character to Kirby and play 5 more matches on Yoshi's Island (melee). After two more, you'll unlock Luigi, and after five more you'll unlock Jungle Japes. Sticking with Kirby, play the next ten matches on Pokemon Stadium 2 to unlock Pokemon Stadium. Now switch to the Halberd and play five more matches to unlock Green Greens. 40 matches total.
Switch to Luigi and play five more matches still on the Halberd. You'll unlock Luigi's Mansion (3 matches) and the Goruda music (5 matches). Next, switch your character to Peach and the stage to Mushroomy Kingdom for 10 more matches. After 3 matches, you unlock the Super Mario Bros 2 demo, after 5 matches, you unlock Falco, and after 10 matches, you unlock the underwater Mario music. 55 matches total.
Play the next 10 matches on those default stage builder stages (character no longer matters) to unlock stage parts A. Play the next five on Frigate Orpheon, and then you'll unlock Captain Falcon. Play five more on Frigate Orpheon, using Captain Falcon this time, to unlock the Metroid Ending music. Switch to Port Town, and after five matches you'll unlock Big Blue and the Peach's Castle (melee) music. Your character doesn't matter anymore, but play five more matches on Port Town to unlock the music track "Dream Chaser". 85 matches total.
Switch to Castle Siege and play 15 matches to unlock the track "Powerhungry Fool" after 10 matches and Lucario after 15 matches. 100 matches total.
Unfortunately, things slow down a bit here. Character and stage don't matter, just play a bunch more matches. After 60 more, you'll unlock R.O.B., and after 100 more you'll unlock Ganondorf. After unlocking Ganondorf, play 50 more to unlock Mr. Game and Watch and Flat Zone 2 and 100 more to unlock Sonic and Green Hill Zone. 300 matches total.
Play the next 10 matches on Green Hill Zone to unlock some Sonic music, and then continue playing matches on any stage until you unlock Jigglypuff (350 matches total) and Toon Link and the Great Sea stage (400 matches total). Play the next 10 as Toon Link to unlock the Ocarina of Time demo and then 40 more with anyone to unlock Wolf, All Star mode, and the Menu 2 music. 450 matches total, and you now have all characters.
Now let's get the remaining stages. Head over to the events and beat event 8 to unlock the Route 1 Pokemon music and keep playing event matches until you unlock the next set. In that set, beat Event 19 to unlock the Mario Bros. stage, event 13 for the Legendary Air Ride music, event 15 for King Dedede's Theme, and event 18 on the difficult setting for the Dark World Death Mountain / Dark Woods music. Play a few more events to unlock the third set. Beat events 25 and 28 to unlock Spear Pillar and the Electroplankton stages respectively. Congrats, you have all stages (as well as the random stage option)!
Based on current unlockable knowledge, this is the quickest you'll get all characters and stages, and you notice you get a lot of other random stuff along with it. I could keep going, but the whole purpose of this was for people who just care about characters and stages so they can just play a lot of multi player. I hope at least one person finds this helpful. I might update this after we have complete information on unlocking everything so more random things can be easily squeezed into the plan. My only concern is that evidently you have to unlock the alternate rules select which is really important, but nowhere seems to have information.