S-Unlocking Jigglypuff: Defeat Master Hand once with any character. Then you will fight Jigglypuff.
S-Unlocking Luigi: Defeat 'Destroy the Targets' with all 8 characters. (Guys you earn don't count) Then you will fight Luigi.
S-Unlocking Ness: Defeat the Game with 3 lives in the normal difficulty. Then you will fight Ness.
S-Unlocking C. (Captain) Falcon: Defeat 1 Player Mode with any character in less than 20 minutes. Then you will fight C. Falcon.
S-Press the L button in battle to do things that don't necessarily help you, but they're interesting.
S-Press R in battle when by opponents to grab them and throw them. Sometimes it will win the battle for you.
S-If you happen to get a small gray disc as an Item, (it's a bomb) throw it in the open and lure opponents to it. If they get too close, the bomb will explode on them and send them flying. Most times it even wins you the battle! Even better, you get a bonus for 'Booby trap'!
S-If a black bomb with a face is an item you get, either pick it up or get away! If you throw it at an enemy, it's a good weapon, but if it walks around, the first thing it hits will be bombed!
S-If your ray gun won't shoot, throw it away. If it won't shoot, it's because it's out of ammo and there's no way to fix it. Throw it by pressing R. If you think it won't shoot, throw it on the ground. If it then disappears in a cloud of smoke, you were right. If it doesn't happen, pick it up and continue play. Hint: When throwing items, try hitting opponents for it will hurt them.
S-Barrels, Boxes, Bottles, Pokéballs: When throwing items like barrels, throw it at opponents. It'll hurt them, and if it's a barrel, then it has to hit something or it'll roll off the edge and you'll lose whatever's inside. If it's over your head, throw it quickly for if someone hits you at all, your barrel/box will disintegrate! Also, any item besides Pokéballs that are listed at the top will sometimes explode when thrown, all the more reason to keep out of enemies' ways.