Story Mode will return in Super Smash Bros. Worlds Collide. It will be known as World's United! Story Mode is also another way to unlock every single character (Excluding DLC Characters and Mii Fighters).
This story starts in a stadium filled with many Toads and Flickies. with Peach and Zelda hosting the tournament and Kirby watching while eating food. The round was between Nintendo's mascot, Mario and Sega's mascot, Sonic.
Battle 1: Vs. Mario/Sonic (Playable: Mario, Sonic)
When the battle is over, Mario/Sonic will be defeated and will turn into a trophy. The character you played as will restore the person you defeated. Then, during the celebration, The clouds will turn dark and black spheres will rain down turning into Primids and attack. Mario and Sonic, along with Kirby, Peach, and Zelda team up to defeat them.
Battle 2: Defeat 30 Primids (Playable: Mario, Sonic, Kirby, Peach, Zelda)
When the Primids are beaten, A dark figure comes out of nowhere with two Goombas activating a Subspace Bomb. The figure flees and Mario tries to stop them until something lands making a dust cloud in the process. Everyone looks to see a cannonball come out of the cloud, hitting Mario, sending him flying out of the stadium. The unknown creature turns out to be Kamella, trapping Peach and Zelda in purple bubbles chained on her back, leaving Kirby and Sonic to fight Kamella and free Peach/Zelda.
Battle 3: Defeat Kamella/Free Peach or Zelda (Playable: Kirby, Sonic)
After Kamella is defeated and Peach/Zelda is freed, Wario comes out of nowhere and prepares to fire his Dark Cannon at Kirby, Sonic, and the princess you rescued until he notices the princess you didn't rescue and turns her into a Trophy, then leaves. The trio chases after Wario until Kirby notices the Subspace Bomb is about to go off and takes the other 2 to the Warp Star and escapes the Subspace Void, Thus ending Chapter 1.
We then cut to Skyworld to see Pit seeing the stadium being consumed by the Subspace Void. Palutena comes in and allows Pit to stop the person doing this. Being equipped with the Palutena Bow, Pit flys out of Skyworld, once again, saving the world, leaving a worried Palutena.
Stage 1: Angel Land (Playable: Pit)
When Pit gets to the end, He looks at a ship passing by. He tries to get a closer look, until a purple bow flies out of nowhere that tries to hit Pit. Pit dodges it and the shooter was Dark Pit who wants to defeat Pit. Pit tries to reason with Dark Pit, but Dark Pit cuts him off, engaging in a battle.
Battle 4: Vs Dark Pit (Playable: Pit)
When Dark Pit is beaten, Pit tries to help him up until Dark Pit slashes him and prepares to finish him until three energy blasts turns him into a trophy. Pit is confused unti Palutena shows up to save Pit's life and they both go away, setting on another adventure. Then a shadow covers Dark Pit and suddenly disappear. The dark figure comes out of the clouds to set up another Subspace Bomb causing it to explode into a Subspace Void sucking Angel Land in it ending Chapter 2.
Chapter 3 begins in the forest with Bandana Dee fishing in a lake. Suddenly, little black puffballs rain down on the forest, being the Subspace Army and Bandana Dee starts to fight.
Battle 5: Defeat 50 Enemies (Playable: Bandana Dee)
When all 50 Primids are defeated, Bandana Dee starts to resume his fishing time, a giant Robo-Primid comes out of nowhere. Bandana Dee tries to attack it, but nothing happens. After one last spear throw, the Robo-Primid begins to chase the Waddle Dee. Bandana Dee had only came up with one option; Run.
Stage 2 :The Forest (Playable: Bandana Dee)
After completing the stage, Bandana Dee is cornered by a cliff. The Robo-Primid is about to attack Bandana Dee, when suddenly Shulk comes out of a nearby bush and stabs the Robo-Primid knocking it down.