It starts off in a cinematic cutscene of Charizard fighting Samus in the Pyrosphere stage. Just as they're both about to clash together, a Mii Brawler of this person shows up and clashes in between them:
http://tinyurl.com/nh4wyp4
He does a taunt pose, and you hear the iconic "Ridley.. is way too big!" (In his voice from the video)
Charizard and Samus look at each other awkwardly, then back at the Mii Brawler. He stands idol for a second, before a shadow identical to the one in the Smash Direct appears above him. It swoops down, grabs the Mii Brawler in his claws, and throws him across the stage. He then lands.
Similar to how Little Mac was shown, the camera quickly pans around various parts of his body until showing his head and the newcomer tagline:
Ridley
is too big for battle!
The tagline disappears, and zooms out to show all 3 characters. Ridley is unusually gigantic, and a size comparison between the 3 is done with a dotted line just like Samus and Little Mac in his trailer. Ridley looks a bit disappointed, but out of nowhere, a bunch of poison mushrooms fall from the sky onto Ridley, shrinking him down to no bigger than Rosalina. He looks at his new body gladly, spreads his wings and screams, with another tagline saying "Ridley ISN'T too big!"
The screen switches to gameplay, with this music playing as Ridley lands on the Boxing Ring stage:
Ridley is shown fighting Charizard and Samus at first on the Pyrosphere stage, along with other gameplay footage. There's a clip showing Ridley flying around a stage while Little Mac can be seen on the ground struggling. Another clip shows him posing next to the Dark Samus and Mother Brain Assist Trophies. Along with one of Ridley fighting the Yellow Devil.
His final smash is shown with Space Pirates raiding the stage. Ridley then shoots fireballs at the screen which then cuts to the Smash Bros logo.
It fades back in to Shokio's Mii Brawler hanging off the Pyrosphere stage from earlier, with Ridley standing in front of him. Ridley makes a scream noise that has a caption under him that says "You've been exposed!" Which he then proceeds to push him off the stage.