Actually, Melee's roster was leaked 20 days before the Japanese release, however, no one believed it at the time. Here is the story of the Melee roster leak:
Melee's roster was beginning to get leaked way back in August, with the first character being confirmed being Ganondorf (I think via an interview), next was Luigi who was confirmed in an interview I think in September. There was much speculation as to whether Jigglypuff would be cut. Jigglypuff was not exactly popular among casual players, and many thought her to be a joke. However, around mid-October, there was a person claiming to know the entire roster. Many people accused him of being a fraud, a liar, etc. He confirmed that Ganondorf and Luigi were indeed hidden characters (some people said that the interviews meant nothing) and that Jigglypuff would be returning as a playable character. He also deconfirmed Wolf as a playable character. The "leaker" then said that he would not reveal the full-roster until a day before Melee's Japanese release. People continually called him a liar and a fake. So he instead decided to submit his story about knowledge regarding the Melee to some GameCube fansite.
This article appeared November 1st, about twenty days before Melee's Japanese release. People were shocked at what the contents were. Luigi, Ganondorf, Jigglypuff, Mewtwo, and Falco were all believable (as well as Marth for the few people that actually knew him). However, what made the list seem like a complete and utter joke was the inclusion of Dr. Mario, Young Link, and Pichu. Mr. Game & Watch also made little sense to many people at the time. Also, many people confused Roy for Roy Koopa from the Mario series. Also, was the fact that more than half of the hidden characters were clones. Many people were upset to discover that Ganondorf was a Falcon clone. The vast majority of Melee forum goers were angry over this and immediately dismissed this as being fake, however, there were a few believers, much like how people who believe Ness is returning are being squashed right now.
This website immediately apologized for the article after the enormous backlash they received from it saying that the information being supplied to them could be very well be wrong. With this, many Smash fans sighed with relief knowing that the nightmare roster was a fake. However, the nightmare would soon resurface in a few weeks. About a week prior to Melee's release, screenshots of the demon roster started floating around the internet. Pictures of Dr. Mario, Pichu, and Young Link in battle were also around. Many of us thought somebody had too much time on their hands, and was doing this for kicks. There was also the point that Melee's clone boxes were misaligned, surely Sakurai's team would not do a sloppy job on the character selection screen. It was also pointed out that there were two empty space on the screen. A lot of people dismissed these screens as being an elaborate fake.
However, when people actually got their hands on Melee and confirmed the worst, many of the naysayers reluctantly accepted that the leaked roster was the real deal. Many people cursed, screamed, saying that they would boycott Melee and threatened Nintendo and HAL for this abomination of a roster. However, when Melee was released many people angers were put aside by how great Melee was.
Here is my personal experience regarding when the Melee roster leaked:
Characters that I liked were Luigi (I wanted him to return), Jigglypuff (ditto), Mewtwo (one of my favorite Pokemon back then), Ganondorf, Falco, and Mr. Game & Watch (I am a big fan of the Game & Watch games).
Characters that I was unsure about were Marth, because I was very unfamiliar with the Fire Emblem series back then. I was also very surprised by the inclusion of a Game & Watch character, but it was awesome nevertheless.
However, there were characters on it that definitely made me think "lol, this roster is fake." They were Dr. Mario (why add another version of Mario and not Wario), Pichu (why not Raichu), Young Link, and Roy. Roy was a funny one. I originally though Roy was actually Roy Koopa and I was liked, "huh, they decided to put Roy Koopa in as a playable character, why did they choose him over the other Koopalings." Then the leaker said that he was actually part of the same series as Marth, Fire Emblem. This was the clincher for many, for there was no known character in the Fire Emblem games that went by the name of Roy at that point in time.
Since so many people flamed the site that leaked the list as being so absurd and nonsensical, they even went as far as to apologize, but said not to be surprised come the Japanese launch of Melee. Many people, including myself, rested easy knowing that abomination of a character list was probably just a hoax for a site to get more hits. However, there were a few that still believed.
Come November 22, 2001, the roster was definitely proven true. The screenshots I saw of Dr. Mario and Pichu were too bizarre to be true, it just couldn't be true, and that Ganondorf was nothing more than a clone of Captain Falcon. Captain Falcon! I was comforted by the fact that somebody pointed out that six of the character boxes were misaligned (the clone boxes), and that there were two empty spots on the screen. Sakurai's team surely would not make a sloppy character selection, and especially not leave two empty places on the screen. Most of us were wrong yet again when videos were finally posted of these characters. Some people continued to deny this, however, many (such as myself) accepted the harsh reality and tried to look at the brighter side of things. However, the character roster did not matter, for Melee was much, much more awesome than I could possibly imagine.
As you can see, I would not be surprised if a similar circumstance happens regarding Brawl's roster. It is also the reason why I am treating many people who claim to have inside information cautiously instead of immediately labeling him or her a liar. Hopefully, the Brawl roster leak won't get as ugly as the Melee one did.
