List of rumors
Like many other games, the Super Smash Bros. series has had various rumors spread about it, usually through the Internet, and sometimes magazines. Most of the time, these will be about playable characters, though occasionally, a different sort of rumor will pop up. The majority of rumors are completely false; others, however, occasionally have a grain of truth to them.
As with any game, the Smash Bros. series has had various works of fan art being passed off as supposedly leaked screenshots. Box art and character selection screens for Brawl were particularly common, though images of characters in the game also appeared. Shortly before and after the release of the game in Japan, these images had become more and more common, though the use of video streaming sites, such as YouTube and Vimeo, had thousands of videos featuring gameplay of Brawl, quickly disproving most of these rumors.
Many character selection screens for Melee also made the rounds; these screens were less credible as the ability to quickly distribute images on the Internet didn't occur until after Melee was released; by then, all the unlockables had been well-known. Some of these fake rosters, however, were merely made as jokes, including a particularly famous image featuring over 108 characters. The inability to easily customise the character roster for the original game has prevented fake rosters from appearing, as there are no empty spaces, and the game was released before the Internet was widespread.
While extremely common, fake character rosters are relatively easy to debunk - for any unrevealed character, they use character images that are either fanart or reuses of images from other games. For example, in the image to the right, Luigi's image is a mirrored version of his official artwork from Super Mario 64 DS.
 Rumors about Super Smash Bros.
 Unlocking non-playable characters
Being able to play as characters such as Metal Mario, Giant Donkey Kong, Master Hand, or a Fighting Polygon was the main source of rumors during the game's era. As with other rumors of the time, the supposed criteria ranged from unusual (spinning the control stick 30 times) to ludicrous (completing the 1P Game as every character in a specific order on Very Hard with a stock of one). Many videos on YouTube continue to claim these rumors, but all of which supposedly work are simply hacks.
 Cut characters
A popular rumor about Smash 64 that came around long after its release was that several characters were planned to be playable in the game, but cut due to time and/or memory constraints. The characters most often rumored to have been planned but cut are Bowser, King Dedede, Mewtwo, Pit, Peach, and Meowth. There exists an official source that seems to confirm that Bowser, King Dedede, and Mewtwo were indeed planned to be playable in Smash 64 but ultimately cut . No such source exists, however, that supports Pit, Peach, or Meowth as having ever been planned to be playable in the game.
 Rumors about Super Smash Bros. Melee
 Unlocking Sonic and TailsMelee remains one of the most infamous not just in the Super Smash Bros. series, but also in the world of video games. An April Fools' joke pulled by the magazine "Electronic Gaming Monthly" said that Sonic and Tails could be unlocked after defeating 20 enemies in Cruel Melee. In a twist, the player was supposed to challenge the two at the same time. The blurb also claimed that upon completing Classic Mode with either of them, the player would get a "special surprise". While EGM was famous for its previous April Fools' jokes, such as the infamous "Sheng Long" cheat, many people still fell for the rumor.
Multiple pieces of evidence debunk the myth:
Following an EGM tradition of having the numbers "1" and "4" in their April Fools' Jokes (as the date is 4/1 or 1/4), the notice commemorating their being unlocked also had the date as "4.1" (April Fools' Day).
Although rival publication Nintendo Power would publish an article about how the rumor was false, without promoting EGM by mentioning them in name, EGM would later confess to making the joke, and like their previous April Fool's Day jokes, mock those who took it seriously. As a prize for people who sent in video proof of getting 20 or more KOs in Cruel Melee, however, they rewarded copies of Sonic Adventure 2: Battle, which was Sonic's first game on a Nintendo system.
Coincidentally, Sonic became a playable character in Brawl, and Tails shows up in cameos. An interview with Yuki Naka, the creator of Sonic, also claimed in an interview that, on the topic of Sonic and Tails appearing in Melee, "it was very close, but time constraints did not allow us to continue with the idea." 
 Unlocking Toad
Another infamous rumor featuring Toad as a playable character in Melee was first spread in November of 2002. The Toad rumor, initially posted on a small independent site that has since disappeared (an archive can be found here), stated that Toad could be unlocked as a playable character in Melee after obtaining a perfect score during the credits mini-game, which is played after completing any one-player mode; after hitting all the credits, the player would then have to clear Adventure Mode (with a requirement of "easily defeating" the Yoshis in the Mushroom Kingdom stage), after which they would be able to unlock him. The site also gave several fake screenshots depicting Toad in various in-game scenarios, propagating the rumor; it came to the point where the images had become more well-known than the site and the supposed method to unlock him, with explanations sometimes varying strongly from the original.
The method has been disproved by the same evidence as the Sonic and Tails rumor; additionally, the screenshots of Toad were made by taking images from Toad when he was running around the Mushroom Kingdom of the Adventure Mode of the game. Inconsistencies with the actual gameplay surrounding Toad also debunked it; the site says that Toad has no accommodations in All-Star Mode, has no trophies, and has no videos for his Ending Sequence after finishing a 1-Player game. The site itself also contributed to the debunking of the rumor; it was hosted on GeoCities, a former web hosting site that allowed anyone to create their own pages, causing the rumor to be considerably less credible than the Sonic and Tails rumor (which was featured in a widely-read magazine). The site is also riddled with incorrect information; for instance, when speaking about the game's Adventure Mode, the site claims that the ordeal is similar to unlocking Falco - Falco, however, is unlockable in Multi-Man Melee, not in Adventure Mode. Spelling and grammar mistakes also riddled the page, such as the misspelling of "taunt" as "taught", and a suspicious "THIS IS NOT A FAKE", causing its already low credibility to fall even lower.
 Lucas replacing Ness
A widespread rumor that came around some time after Melee's release was that Masahiro Sakurai planned to replace Ness with the new protagonist of Mother 3, Lucas. This rumor was confirmed by Sakurai himself, where he stated that he was going to replace Ness with Lucas, but time constraints caused him to go back on the idea and keep Ness in.
Relating to this rumor, after Lucas was confirmed to be a newcomer in Brawl, it was speculated that Ness would not return, being replaced by Lucas, as was originally planned in Melee. Such speculation ended up untrue, however, as Ness returned again as a playable character in Brawl.
 Solid Snake in Melee
A widespread rumor claims that during Melee's development, Hideo Kojima, a good friend of Sakurai's and creator of third-party game franchise Metal Gear, practically begged for Sakurai to add him into the game. Unfortunately, the game was too far in development, so Snake was added into Super Smash Bros. Brawl.
 Rumors about Super Smash Bros. Brawl
 Additions and removals of characters
At one point shortly after Brawl's announcement, a rumor began floating around that in a radio interview, Masahiro Sakurai confirmed that Ridley, a cel-shaded Link (Toon Link), and Bowser Jr. would be playable characters. Coinciding with this was the rumor of Young Link, the Ice Climbers, and Mr. Game & Watch being dropped. This was proven to be false; while Toon Link does replace Young Link in Brawl, Ridley appears as a boss instead of a playable character, Bowser Jr. only appears as a sticker and trophy, and Mr. Game & Watch and the Ice Climbers do return as playable characters in Brawl.
 No more clones
Another popular rumor stated that Sakurai claimed clones will not be in Brawl. That would mean Dr. Mario, Roy, Pichu, Ganondorf, Falco, Young Link, and (to a lesser extent) Luigi, would be either removed or redesigned for Brawl. Despite initially being unbelieved, the rumor became notable for having truth to it; Ganondorf and Falco returned, but with considerable differences from Melee, distancing them from the original characters of Captain Falcon and Fox respectively. Luigi had multiple changes to his character as well, though the original of Mario also had a few changes. Dr. Mario, Roy and Pichu were completely removed, though data for the former two exists in the game. Young Link was also removed, though he was essentially replaced by Toon Link; Toon Link, however, still has many differences from Link, and is not as complete a clone as Young Link was. Additionally, of the 18 new playable characters added, only Toon Link and Lucas had some considerable sort of cloning, and were semi-clones rather than complete clones. Overall, Brawl has no complete clones and five semi-clones out of 39 playable characters, compared to Melee's six complete clones and one semi-clone out of 26 playable characters, thus validating the rumor by having significantly less cloning.
 Sukapon, Animal Crossing characters and Mii
Sukapon from Joy Mech Fight was a heavily requested character for Melee and Brawl; Sakurai stated that this would not happen, though he promised the very disappointed fans that Sukapon would be included in the latter game as a trophy. (citation needed) This did not hold true, though Sukapon makes a cameo as a sticker.
Another rumor suggested that Miis and a character from Animal Crossing, such as the generic playable male/female character (termed an "Animal Crosser") or Tom Nook, would be playable in Brawl. Sakurai disproved this rumor, stating that "On one hand, they have an innocent charm to them that could be ruined if they were in a fighting game" (however, he would later go back on this statement, adding Villager as a playable character in Super Smash Bros. 4). Despite the lack of a playable character, Animal Crossing is strongly represented in Brawl by multiple songs, trophies, stickers, an Assist Trophy, a stage, and numerous cameos on said stage. Miis can also be used as avatars through Wi-Fi brawling.
 A third third-party
Sakurai said that, after Sonic and Snake, there might be a third third-party character; prior to Sonic's announcement, he also claimed that "one or two" other third-party characters would appear. This led many people to believe that it was certain that another third party would be included.
 Capcom's Mega Man
One of the most popularly-rumored characters was Capcom's Mega Man, from his own self-titled series. The inclusion was considered plausible due to Mega Man having a very strong history with Nintendo consoles, as well as a resurgence in popularity with the Mega Man Anniversary Collection for the GameCube. Rumors claimed that a Japanese website from Nintendo was asking players which third-party characters they wanted to see, with Mega Man being second-most requested (behind only Sonic). No website, however, is known to exist to prove this.
While Mega Man didn't appear in Brawl, he was eventually introduced to Super Smash Bros., being included as a playable character in Super Smash Bros. 4.
 A second Sonic the Hedgehog character
After the announcement of Sonic appearing in Brawl, another rumored third-party brawler was another character from the Sonic the Hedgehog series; Tails, Knuckles, and Shadow were the most commonly speculated, as Tails was Sonic's partner and close friend, Knuckles was a partner and rival, and Shadow was among the most popular characters in the series. Additionally, all three had been playable in the Sonic series. While they did not become playable, Tails and Knuckles appear in cameos on the Green Hill Zone, while Shadow appears as an Assist Trophy.
 Geno rumor
A popular rumor among some fans is that Nintendo had negotiated with Square Enix to receive a license for the inclusion of their character Geno, from Super Mario RPG: Legend of the Seven Stars (a game which was developed with Square, who disallowed direct sequels to the game without their permission or involvement), as a playable character in Brawl. This rumor suggests that Square declined to allow Geno's appearance, or they demanded a large amount of money to allow him. The rumors go as far as to suggest that the Random Character box on the character select screen was intended for Geno, which ties into the fact that it is located under Solid Snake and Sonic, both third-party characters, and a dedicated "random character" box has not previously been featured in the series. There is no evidence to support such a rumor, as not only is there no unfinished character package labeled "Geno" present in the game's data, and there is no Super Mario RPG-related content in Brawl whatsoever.
 Leon S. Kennedy's voice actor and Brawl
The IMDB page for Super Smash Bros. Brawl listed the voice actor Paul Mercier as one of the many voice talents recruited for the game; Paul Mercier's most well-known role as a voice actor was Leon S. Kennedy of Capcom's Resident Evil 4. Some fans claimed this gave evidence to Kennedy appearing in Brawl. Leon's possible appearance was considered plausible by these speculators; while he appeared in M-rated games, Snake had also done so, and he had appeared more often and more recently on Nintendo consoles than Snake: Kennedy appeared once on the Nintendo 64 in Resident Evil 2, two times on the GameCube for a port of Resident Evil 2 and the original game Resident Evil 4, once on the Wii for a remake of Resident Evil 4, and once on the Game Boy Color for Resident Evil Gaiden. IMDB, however, allows anyone to contribute content, so this rumour was overall not credible. Mercier's name was later removed from the listing, and Leon does not appear in the game.
Relating to the Megaman and Leon S. Kennedy rumors, Sakurai has recently said, in relation to the fourth Super Smash Bros. game, that he "can't say that it's entirely out of the realm of possibility that some Capcom character could appear in the next Smash Bros." Capcom's Yoshinori Ono also has stated he has an interest in creating a Nintendo vs. Capcom game, in a vein similar to the Marvel vs. Capcom series. 
Megaman was announced at E3 2013 to be in Super Smash Bros. 4, although it was not announced as to whether or not he is the only Capcom character in the game.
 Downloadable content rumor
Shortly after Brawl was released in America, a newspost appeared on the Internet, claiming that Brawl would feature four downloadable characters and two downloadable stages, as well as a new Wii Channel of "Wii Want More". The discovery of multiple unused character files present in the game also added fire to the rumor, under the assumption that the empty files render it easier to create add-on content.
The rumor was quickly proven as false; Masahiro Sakurai himself stated that downloadable content would never be coming for Brawl, as the Wii's flash-based internal hardware is incapable of patching or otherwise modifying a game based on a downloaded file. The supposed release date of May 13th, 2008 also passed without a "Wii Want More" channel being released or announced. Additionally, in a vein similar to the Toad rumor, the site was hosted on 110MB, a hosting site where anyone on the Internet can publish content.
 Brawl is the last game
During the development of Brawl, Sakurai reportedly said statements along the lines that he was making Brawl as the last game; additionally, some advertisements had the tagline of "One brawl to end them all!". This led several to believe that this is the last game in the series. The rumor, however, is taken out of context; Sakurai stated he was making Brawl like it was the last game, not that it was the last game. Additionally, Sakurai said that Melee would've been the last game on Smabura-Ken, and that did not hold true. This rumor was ultimately proven false at E3 2011, where a new Super Smash Bros. title was announced for both the Nintendo 3DS and not yet released Wii U consoles; development started in February 2012.
 Rumors about Super Smash Bros. 4
 Super Smash Bros. Universe rumor
Shortly after the official announcement of the fourth Super Smash Bros., an image circulated around the Internet detailing what appeared to be an advert or design document that was said to be from the official Nintendo headquarters in Japan for Super Smash Bros. Universe; multiple imageboards worked to translate the document, leading to some supposed preliminary idea for the games. However, Sakurai stated that he hadn't begun working on the new Smash Bros. at the time and was focusing on Kid Icarus Uprising.
 '"2 out of 3'" rumor
Shortly after the release of Kid Icarus Uprising, a multitude of screencaps appeared on All is Brawl, showing a conversation on social site Twitter between Sakurai's official account and a Canadian fan. The conversation began with the fan asking for Geno from Super Mario RPG, Isaac from Golden Sun, and Mega Man from his eponymous series to appear. Sakurai's response was "2 out of 3", which the blog author claimed gave credence to the possibility of two of the three aforementioned characters appearing. However, the author also claimed that the Tweet in question from Sakurai was deleted only half an hour after being posted.
The rumor was proven false almost immediately; the most telling was a comment which showed that in both Sakurai's real Twitter feed (where the Tweet did not appear) and the image showing Sakurai's feed with the "2 out of 3" Tweet both had a Tweet count of 8807. The plausibility of the situation of Sakurai revealing very notable information, then immediately retracting it, was also doubted.
 Super Smash Bros. Memories rumor
According to an anonymous source who wrote to Zelda Informer, Super Smash Bros. 4 for the Nintendo 3DS would be called Super Smash Bros. Memories. The letter outlined that Nintendo has confirmed that both Super Smash Bros. games – for Wii U and Nintendo 3DS - will not be identical, and the source also claimed that it knew the main difference between the two.
According to the rumor, Wii U's Super Smash Bros. would focus on modern characters while Super Smash Bros. Memories would star retro characters, such as Donkey Kong Jr., Ridley, Pac-Man, Takamaru, Mach Rider, "Dig-Dug", and Stanley the Bug Man. The source also claimed that Nintendo would put the game on store shelves in the fourth quarter of 2013, around December.
This rumor ended up proving false, with the E3 2013 reveal showing that the main difference between the two versions of the game is not between characters, but between stages: the 3DS version's stages are mainly based on handheld games while the Wii U version's stages are mainly based on console games. It was confirmed later by Sakurai that both versions will have the same playable cast. The rumor's set timeframe of Q4 2013 was also proven false, as the game is currently set for release sometime in 2014.
 "Namco worker" rumor
Another rumor popped up on Gamefaqs by a user named Halibuton, claiming that he worked for Namco and had some information told to him by his co-workers.
He reported that there would be a Nintendo Direct on the fifth anniversary of Brawl's Japanese release (January 31) and said it would be centered around Smash 4, though likely more of a series retrospective with minor new info than a full-blown reveal trailer. He also said that he knew a bit about the early roster and claimed to know a few newcomers: Takamaru from Nazo no Murasame Jō and Little Mac (chosen as recent-popularity classics and an "East vs. West" concept supposedly due to previous games being too Japan-only-series-centric) as well as King K. Rool and Ridley (chosen due to popular demand and having movesets based on more recent games). Other claimed, less-finalized newcomers are Shulk from Xenoblade, Dillon from Dillon's Rolling Western, Ghirahim from the Legend of Zelda series, a "Debu" from the at the time rumour-only Yarn Yoshi (supposedly a partner of Yoshi, with "Debu" possibly being just a nickname or placeholder), and a Platinum Games character possibly from The Wonderful 101. Aside from characters, multiple stages were listed: Starship Mario (Super Mario Galaxy 2), Giant Chasm (Pokémon Black 2/White 2), Pushmo Park (Pushmo), and Cookie Country (Kirby's Return to Dream Land).
 Lucina rumor
An AllIsBrawl post made early on the 25th of June 2013 claims that an image had been leaked on the Smash 4 website, presumably from the "image of the day". The image shows Mario and Lucina (from Fire Emblem Awakening) on a Fairy Isle in the Great Sea. There was no evidence on the site, however; the image of the day was Link doing an aerial Spin Attack in Skyloft.
This image, while appearing to be legitimate, is actually compiled using a variety of elaborate hacks available for Brawl. The stage seen in the image looks exactly like this Fairy Isle hacked stage, and the Mario in the image uses this texture hack to make his model more closely resemble his newer model in Super Smash Bros. 4; Lucina herself is identical to a PSA hack seen in "The Lucina PSA". While not particularly widespread outside AllIsBrawl, this was the first known rumor to showcase the level of elaboration that Brawl hacks bring to rumor producers.
 Ness and Jigglypuff rumour
On November 2013, 2 supposedly leaked images of Ness and Jigglypuff in Super Smash Bros. 4 began circling around the Internet. One image was the "official" artwork of Ness for SSB4. The other picture featured both Ness and Jigglypuff standing on the Battlefield stage in the 3DS version.
While the photos appeared to be legitimate, they were confirmed to be fake shortly after with analysis showing several inconsistencies between the purported leaks and known originals.