Here are some examples of this spectacle:
Ness and Jigglypuff LeakAround the end of 2013, two images of "Original Twelve" characters, Ness and Jigglypuff. One picture specifically of a site artwork for Ness and the other of Ness and Jigglypuff on Battlefield in the 3DS version. These eventually turned up fake but still achieved the community's attention.
One reason they looked fake were because of some shadowing that doesn't look like an actual 3DS version picture. Though it is possible the screenshot was from early development.
In early 2014, some images started appearing on the web of (now confirmed) character Palutena. When Palutena got confirmed in the E3 2014 event, her model changed slightly but not enough to call this image a clear fake.
Falco LeakAround February 2014, someone posted two images of Falco; one on the site and one in gameplay. These images were eventually proven fake come the next reveal, Little Mac.
Rayman Character Trophy
On August 1, 2014, Nintendo of Canada employee, Matt Ryan leaked a third party character, Rayman.
"So Pac-Man is one of the new characters we announced at E3 2014, people are pretty excited about that, most excited about that. Rayman and a whole bunch of others."
This turned out to be a mistake when Nintendo corrected him a few days later that he was talking about the trophy of Rayman.
Character or unlockable details follow. Venture at your own risk
The Gematsu Leaks were a text leaks that turned out to be mostly true.
|Playable?||Reveal Date||First Leaked Date|
|Villager||Yes||E3 2013||E3 2013|
|Mega Man||Yes||E3 2013||E3 2013|
|Wii Fit Trainer||Yes||E3 2013||E3 2013|
|Little Mac||Yes||February Direct||E3 2013|
|Pac Man||Yes||E3 2014||E3 2013|
|Shulk||Yes||August Direct||Smash Direct|
|Palutena||Yes||E3 2014||Smash Direct|
|Chrom||No||April Direct||Smash Direct|
|Chorus Men||No||Japanese Leakers||Smash Direct|
|Greninja||Yes||Smash Direct||Smash Direct|
|Mii Fighters||Yes||E3 2014||E3 2014|
Most likely the biggest and most recognized leak of all.
On 8/25/14, a leak for Super Smash Brothers For Nintendo 3DS was shown to the public, having videos to go along with it. Many characters were shown, including the Duck Hunt Dog, A.K.A Mr. Peepers in the form of a screenshot, which many thought was fake. Then eventually, somebody uploaded some leaked footage of Shulk and Bowser Jr. being used. However, Nintendo found out about the leak, and deleted the footage for copyright infringement which sparked the SSB community into thinking the leak was true. The leaker was apparently an employee at Nintendo of America. The leaker was then fired from Nintendo of America, and was then sued. People in the Super Smash Brothers Series Community were debating wether the leak was fake or real, leading to many arguments.
But on 8/26/14 and 8/27/14, Sakurai showed some POTDs revealing more menus which looked exactly like the leaked menus, thus proving the leak to be possibly be true.However, on 8/29/14 Shulk was confirmed to be playable, along with having the same render and fighting style that was shown in the leak, confirming the leak to be true.