Check the cheats section for information on obtaining the secret characters.
Dr. Mario is one of the six clone characters. His abilities, weaknesses and moves mirror that of another character, Mario. The only slight difference between the two is that Dr. Mario shoots Megavitamins instead of Fireballs, and wears a doctors overcoat. The other differences are hardly noticeable.
Luigi, like Dr. Mario, is essentially a clone character, except he's not considered one because his character dynamics are different. His shape is different, he slides more than Mario, some of his moves are completely different, playing Luigi is like playing an all together different character than Mario. Luigi's Up-B doesn't make coins appear, it's called the Fire Punch, and if you can hit a character with it at the right time you will do massive damage and most like send the player off the top of the screen. He also doesn't carry a cape. His B-forward move is a lot like Pikachu's and Pichu's. It sends Luigi hurling a little ways across the screen, and can be used to help get Luigi back on the stage when sent flying.
Ganondorf is the second of the six clones. He generally mirrors Capt. Falcon. He too has a power punch for his B move, a little more powerful however. Ganondorf has barely any jump though, and is a very slow character with limited moves. It takes and expert to use or want to be this character.
Falco is the third of the six clones. Falco, however, is least like the character he mirrors. Compared to how close all the other clones are to their original characters, Falco has many differences from Fox. With him being a bird, he falls much slower, moves a little slower and jumps a little higher. His Laser has the ability to stop people in it's tracks while Fox's only added percent while your opponent kept coming at you. One fault though is that Falco doesn't have Fox's ability to rapid fire his laser. Falco also has a larger reach with many of his moves.
The fourth clone of the six. Young link is obviously the clone of Link. His moves are all the same with very few differences. He has a much shorter reach with his moves, and can't jump quite as high. The only advantage he has over link is his agility and one of his specialized attacks. Young Link's arrows have fire. Not much to make you want to use him...
The fifth of the clones. Pichu is a clone of Pikachu. Pikachu is actually the evolved form of a Pichu. With a Pichu being the earlier state, it's also the weaker state. Anytime you use an electrical move with Pichu it actually causes Pichu to give himself percent. Not only do you have to worry about not getting hit, but you then have to worry about not killing yourself to quickly. The only advantage Pichu has is agility.
Yes, she's in this game too. A lot of people jump to the conclusion that Jigglypuff sucks.....they were right.......wait, wait, perhaps I'm judging to harshly. If you actually give Jigglypuff a bit of a chance she's not all that bad. She racks up a ton of percent when she hits people and has the ability to puff, but that doesn't make up for her bad aspects. Her new Tap-B move sucks....badly. She still flies off easily and still lacks an effective Up-B move for getting back onto the stage. A below par character.
Another Pokemon in Super Smash Bros. Melee. Some would say its to much. This Pokemon looks absolutely sweet, which is way more than I can say for his moves. Mewtwo can float, and when you Tap the control stick and run he hovers through the air not touching the ground. He picks up items with his mind. When he picks them up, they float in front of him. Almost everyone who sees this character wants to be him. Then they have to control him for a while. You soon find out that Mewtwo's floating ability allows him to fly off quite easily. Although he has massive jumps and hardly ever has to use his Up-B move to get back on, it's a good thing. His Up-B move does no damage. Every single one of his B moves has no range. No range at all. Mewtwo can't hit people behind him. You have to turn around or roll to get an enemy back in sight, cause all his attacks are forward. After time, all players soon realize that Mewtwo is all bark and no bite.....damn....I wanted to be him :)
Mr. Game and Watch
The name makes Mr. Game and Watch sound like two characters. Nope. He's a 2D Black character off an old Nintendo game. All his moves have sound effects of tons off of the old game. It's quite annoying. Although his moves do a ton of damage they are plagued with a devastating predictability. Anyone can see his moves coming. With lots of practice, one could learn to defeat anyone with this character...over time.
Prince Marth is basically a regular human wearing a cape and fighting with a sword. He looks and sounds powerful, but that's just the thing. He doesn't have a single move that doesn't involve his sword. The other crap factor is that You can't hit anything with the sword. Prince Marth's sword has a specific point where you should hit the enemy. The tip. When you do it can do a lot of damage. Some of his B moves are pretty cool too. His Tap B sends him into a combo attack that can do devastating damage.
The final of the six clones. Roy is the clone of Prince Marth. These two characters come from the same game and look almost the same. Roy is younger than Prince Marth though, and it sounds this way to in his voice. His moves are very similar to Prince Marth's except much more powerful. He can do up to 50% with one attack if fully charged. The one thing that is difficult to get used to is the contact point on his blade is right in the middle (Translation: You have to be closer to enemies to be able to hit them)