CONFIRMED REAL MORE OR LESS.
WE NOW HAVE VIDEOS!
First off, the text leak.
This came first, and was posted to Smashboards last month. It's in a members-only section, but here's the main meat of the Ninka/Vaanrose Leak as it's called:
It was posted by moderator Neo Zero, who, as proof, was PM'd pictures of a Brawl Mod that showed alternate colors for Mario and Bowser, claiming said colors would appear for real in the Smash 4 E3 Demo/Best Buy Demo. These pictures were made June 6th.
So I got more info...
Unless my friend is pulling my leg, there's some pretty crazy crap left to be revealed.
-Snake, Lucas, Ice Climbers (Why), and Wolf are cut
-Doctor Mario is back as a clone
-Dark Pit is a newcomer as a clone
-Each character gets 8 alternate costumes, whether they be pallet swaps or new costumes.
-Alph appears as 4 of Olimar's costumes, while the other 4 are Olimar's.
-Shulk will be playable with Gaur Plains as his stage, his neutral B changes his Monado mode which essentially makes him dish more damage and take more, or do less damage, and take less.
-Bowser Jr appears as a new comer and allegedly fights from a mario kart... has no alt colors, but instead has the 7 koopalings as alts.
-Duck Hunt is in... from what I've been told it's the duck hunt dog fighting with ducks on his back who assist for certain attacks...
*Edit more info
-Shulk has like 5 different mode swaps
-Bowser Jr rides in a koopa kart that attacks with cannon balls and boxing gloves and stuff that eject from the clowns mouth. This was later specified to be the Koopa Clown Car Bowser Jr. rides in NSMB
note* The kart sounds more like the koopa clown car to me as I read it.
Now I'm not even sure from this stuff so take it with a grain of salt, but my friend recently quit as a tester due to family reasons, so if he decided he no longer cares what leaks, I could see why he'd tell me.
He was also unclear to me as to if that is the rest of the roster so also be wary.
Quite a few Smashboard Mods vouched for the text rumor, but overall, it sounded a bit off. First of all, Alternate Colors wouldn't be that hard to guess, and there'salways a possibility that the person who sent the pictures had early access to the Best Buy Demo and fabricated a more detailed leak based off simply one bit of early information. There was also a rumor that Smashboard Mods made this leak up as a litmus test, posting it as a supported leak to trick would-be-leakers into exposing themselves as frauds if they included Duck Hunt Dog or Bowser Jr., but this rumor was never supported by any Smashboard Mod coming out and saying that this leak was definitely a fake.
As of yesterday, the leak took a surprising turn when very interesting pictures appeared in a 4chan thread on /v/, basically out of nowhere. They have been claimed to be an ESRB copy, however, the ESRB does not receive the games early according to their site, instead they are merely sent a video showing the game's notable moments and rate it from that. However, the theory here is that the leak comes from a Treehouse employee who took the footage and submitted it to the ESRB. Or something like that. We really don't know WHERE these images come from, and the identity of who the leaker is is still a bit blurry.
There are three waves of the picture leak, these are all the pictures and which wave they belong too...
Leak 1 was first posted to /v/, although a bit beforehand a thread popped up showing just the character icons, not the full CSS. An hour or so later, these three pictures showing the Character Select Screen appeared. The trip that posted one of these pictures, before anyone else had posted it, also later said the main missing Veterans, and Chorus Kids, were DLC (possibly released when the Wii U version comes out). A member on Smashboards later claiming to be the leaker also claimed that he only posted the CSS and the DLC Post, thus putting later pictures as belonging to a different leak.
Leak 2 was posted in the same /v/ thread, and not too long after the first batch of pictures. Because the DLC post says "my friend will stick around", and the Shulk and Dr. Mario models match the head portraits on the CSS of the first leak, it's believed that these are probably authentic as well. It shows what looks to be a Start Screen with the characters scrolling by, and the Stage Select Screen.
Leak 3 was posted LONG after the other leaks, and on GameFaqs. While the first picture looks alright, the in-game screenshot appears to simply be a Brawl Mod. It's strongly believed Leak 3 was a different person piggybacking off the original leak due to the time and location differences. I consider them to be fake.
There is also a Leak 4 right now, where a few Smashboard mods are now claiming that the Character Select Screen is authentic, but, they've offered no proof beyond their status as mods on a popular forum. Some people think this whole thing is a giant prank by Smashboards in fact, their best members working on it.
Now, I'll go over some popular speaking points for and against its legitimacy...
* Tomadachi Life: The room shown in Stage Select Screen matches a room shown just today in Famitsu in a shot of Tomadachi Life. The room has never appeared in any other shots of Tomadachi Life.
* Original Renders: Although some of the renders do resemble pre-existing renders, the models of Bowser Jr., Ness, Duck Hunt Dog, Shulk, and Dr. Mario, which we have the clearest view of, have not been found anywhere else on the net. There's a picture going around suggesting Shulk is an altered Little Mac pic, but, personally...
...it seems like a bit of a stretch.
* The "Thick Line": This actually began as an AGAINST! claim, but notice on the pic with Bowser, Bowser Jr., Pikachu, and Kirby, there are thicker lines beneath Bowser's P1 and Kirby's CPU. A mistake by the leaker, right? Not so, it's been discovered that the thicker lines occur in the actual game as seen in videos of the demo, a fact basically no one noticed till after this leak occurred and people were looking for it. Something no one noticed, and most people would see as a mistake, the "faker" managed to include.
* Character Select Oddities: Why is Yoshi stuck between the main Mario characters? Why is Shulk with the 3rd Parties when Xenoblade is technically 1st Party? Why do the new clones have their own little corner while Toon Link is with his own series? There seems to be gaps, suggesting there are more characters to be unlocked, which might shuffle around the icons and make them fit better. Also, no names. However this seems odd...anyone making a fake leak would notice the roster has names, so the lack of them is a really big omission for a faker to miss. Perhaps the names disappear after unlocking enough characters for space, or were just included for the benefit of the demo.
* Meta Knight: Such a detailed leak seems like it took some time, and it's interesting that a character model just revealed last week is here. Whoever made this leak had a small margin for error, as any new veteran reveal, or an Assist Trophy of one of the newcomers, would totally destroy it. Hell, it could've happened last night! You would imagine the leaker, if he wanted to get the most mileage out of this leak, would've leaked it on a Friday so he'd have all weekend as a safe zone.
* Duck Hunt Dog: Such an odd character...people joked about using him since the Melee days, but no one ever seemed to seriously consider him. He certainly fits the rumored "Retro Revival" character that Sakurai supposedly wanted to include. Furthermore, like Villager, in Brawl Sakurai mentioned the prospect of Nintendog being a fighter but decided against it...perhaps he found that the original Nintendog would work even better?
* Dark Pit: Dark Pit made a mysterious appearance at the end of the Palutena Trailer, but was not elaborated on. A Boss? An Assist Trophy? A simple alt for Pit? Well, this leak suggests he's like Lucina, a quick clone character, which means he'd be the first Newcomer to actually appear in a trailer before his official debut.
* Doctor Mario: Out of all the Melee cuts, why bring back him? Roy just got a new design in Awakening, Pichu had a few promotions not too long ago thanks to HG/SS, and Mewtwo got a new movie and Mega Form. But then it hit me...since Brawl, Dr. Mario has had appearances in multiple digital download games like Dr. Mario RX and NES Remix. Could he be returning to represent the "EShop" portion of Nintendo? Furthermore, with Mario having F.L.U.D.D. now and Luigi changing up, Dr. Mario could serve as the closest version to the original Smash Mario now.
* Shulk: Gematsu mentioned him, and he seemed like a good choice. He's got a new game (well, his series, we don't know if he appears) being advertised, and the one Monolithsoft guy has been repeatedly re-tweeting any Nintendo Directs with Smash, including the day we got Robin and Lucina, as if he's expecting someone to appear...fake or not, I think Shulk's in.
* The Stages: Although the Stage Selection Screen might not be part of the original, authentic leak, it does seem a bit...off. The only new stages shown are the full shot of N's Castle, an F-Zero stage that seems to just use the SNES game as a background, the GB Stage hinted at the other day which seems to be based on Kirby's Dream Land, and what seems to be Magicant from Mother and Gaur Plains from Xenoblade. Many series don't get new stages, a lot are just pulled from Melee and Brawl like Jungle Japes and Corneria. Then again, we've yet to see a new DK or Metroid Stage in the 3DS Version, while Jungle Japes and Brinstar, which was just confirmed yesterday when this leak was post, have been confirmed to be in the 3DS Version. Jungle Japes also appears in Classic Mode, where in Melee and Brawl Classic Mode never used retro stages iirc, suggesting the Retro Stages in Smash 4 are going to be the "main stages" for some franchises.