For this game the maximum damage count was raised, not only that but new functions were introduced: Critical Strikes and Critical State, once your damage count passes a certain limit, as it gets redder you'll have more chances of landing a Critical Strike, which would do more damage/knockback, if you reached a certain amount of damage and you haven't been defeated you'll reach Critical State, where Critical Strikes will become so frecuent almost every attack will be a Critical Strike, but of course this is at a point where your character has a really high amount of damage, making the chances of getting defeated really high. When you're in Critical State your character's image at the bottom will turn slightly red-ish and your character will flash red every so often, his idle animation also changes to make the character look more tired.
In terms of returning features, most features of the Smash Bros. franchise do return, except tripping (unless you use a special item) and Stickers, there were plans for a Subspace Emissary-type story mode but the develpres decided not to include it in the game, the artstyle is changed so that it resembles Meelee more, which means characters and stages become more colorful.
The developers had thoughts of scrapping Final Smashes from this entry to make it more simple but decided not to do it in the end.
In this mode up to 4 players can team up and tackle a randomly generated dungeon inspired on the original Legend of Zelda for the NES, as you go along you also find upgrades and items to help you fight enemies and even bosses.
It shows a kid playing MK7 on a New 3DS while other kids watch, until a new screen pops up to the left of them with a brand new game, the kids start slowly walking to it until the New 3DS starts shaking and finaly flashes, revealing SSBC's Title Screen, the kids come back to the New 3DS and one of them, hesitant, grabs the 3DS and presses start, then a bright flash covers the screen and it cuts to gameplay.
Eventually after showing the veterans fight off in New Battlefield, Mario gets the back of his shirt cut in a pattern that says "LOSER", the other fighters laugh and Mario examines it closely, finding some leaves in it, then Mario gets hit off-stage by a Sceptile who then quickly runs to Brendan's side, "BRENDAN BECOMES THE OMEGA MAN!", then it show gameplay of him before showing his Final Smash.
After the trailer ends it shows in a post-credit scene Link taking a walk until he finds something on the ground, he pick it up and it's revealed to be a pixel, the pixel then turns into Link's sprite from the original game, making Link drop it, then the sprite turns into a normal character that looks like Link's artwork from the first games, he then smiles at the camera and the trailer ends.
The trailer opens where the last one left off, Retro Link then jumps and poses, "RETRO LINK STARTS THE LEGEND!", then Retro Link and Link start walking until they find a dungeon, they call all the other characters and they all go inside, then it cuts to gameplay of the new mode, "Dungeon Crawlers", then after a while a big swarm of enemies pop up in a room and Retro Link uses his Final Smash which defeats all the enemies.
Then in a post-credit scene Retro Link looks around lost when all of the sudden a stork pops up and points him in the right direction, Retro Link smiles and starts walking that way until noticing that he just saw a stork in a dungeon, he then quickly looks back and sees he's not there, Retro Link then walks away with a confused face.
Chaos in the Explosive Maze!
First it shows Wario walking into a maze with Gameboy graphics like in Wario Blast! then Wario starts throwing bombs until he throws one at a door which blows up, which reveals a live-action adoption center, the explosion causes all the babies to cry and Wario starts running, the stork from Yoshi's Island flies in the room and calms down the babies before chasing after Wario, "STORK FLIES IN!", then it cuts to some gameplay of the Stork in the new stage, Wario's Explosive Maze, then it shows the Stork's Final Smash and the trailer ends.
In the post-credit scene it shows Stork helping with the babies, once he's done, he leaves the room only to see Bomberman chasing Wario around the maze, startling the Stork and making him fly away.
Anti-Gravity, Go-Karts and Fighters, oh my!
It shows a normal MK8 race with Toad on the lead until he crashes into Bomberman, who in anger, blows up his kart, "BOMBERMAN BOMBARDS THE BATTLEFIELD!", Toad finally lands back down on the ground and goes into fighting stance, "TOAD RACES IN!", then it cuts to gameplay in Mario Kart Stadium until Bomberman uses his Final Smash which almost blows Tad off, then Toad uses HIS Final Smash, which manages to defeat Bomberman, Toad celeberates until a kart comes by and sends him flying.
In the post-credits scene it shows Bomberman landing in a pagoda, interrupting Takamaru's meditation, however Takamaru decides to ignore him and starts meditaitng again until Toad lands on him.
Mess in Murasame Castle!?
It opens with an unconscious Takamaru waking up only to see his pagda completely destroyed by Bomberman and Toad fighting, Takamaru jumps into action, "TAKAMARU SNEAKS INTO BATTLE!", then it cuts to gameplay in Murasame Castle stage until Takamaru finally shows his Final Smash.
In the post-credits scene Takamaru is meditating while Bomberman and Toad, injured, are fixing the pagoda, when all of the sudden one of the floorboards break and Toad falls through it, then Takamaru opens his eyes and quickly looks at the hole and says (in japanese) "You'll have to fix that" before closing his eyes again.
A Trailer About Mii
Toad wakes up and notices that he landed on a small underground hole below the floorboards, however he notices that the floorboards he fell through are fixed which means he's stuck down there, that's when he sees 4 strangers trying to light up a torch, once the torch is finally lit it is revealed that they are the Mii Fighters, however, they see one more Mii Fighter, the Archer Mii, then the three start to fight against the Archer Mii, and in the process they break the floorboards again, Toad escapes and Takamaru tries to beat them again but gets run over by the 4 Miis, then it cuts to gameplay of the Archer Mii until showing his Final Smash, the Miis decide to take the fight outside, and they crash on Mii Plaza, where they manage to anger a Ninja Mii who fights back using his Bo stick, then he uses HIS Final Smash.
In the post-credits scene it shows Toad running away from the fight until he finally reaches a safe spot, until a spaceship crahses into him, and form out of the spaceshipo Samus Aran jumps out as a beast crashes down after her and destroys her ship, Toad comes out of the rubble to help Samus fight the unknown giant beast.
One Final Quest
Master Hand and Crazy Hand tells all of the characters who have been revealed so far, who are in a picnic, that they have to travel to the many different worlds in order to stop a mysterious villain, then he opens up a portal and the characters jumnp through it, and then it cuts to the brand new Adventure Mode, "The Multiversal Quest".
In the post-credits scene, the mysterious villain's shadow is shgown until he notices the camera and covers it.