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).
It was a regular day in the Mushroom Kingdom whee everything was normal, until an explosion near Peach's Castle appears and soon a fleet of airships. Mario sees this outside his window and warns Luigi that the kingdom is under attack. They both then run out of the door to Peach's Castle with a shadow watching them from a bush.
Stage 1: Mushroom Kingdom; Clear the stage. (Playable: Mario, Luigi)
After Mario and Luigi enter the castle, they find Bowser holding Peach in his grasp. Luigi cowardly hides behind a pillar, leaving Mario and Bowser to fight.
Fight 1: Vs. Bowser; (Playable: Mario)
After defeating Bowser, a loud boom is heard from outside. Everyone runs outside to find a giant ship storming the town. The ship, AKA The Subspace Battleship, then charges and shoots a laser so large, it reduces the castle into rubble. Then it sends out a giant claw that grabs Peach. Mario and Luigi try to reach it, but it is to high. The ship then recalls it's minions and then it heads out to another place with Mario and Luigi on the run.
Meanwhile in a canyon, Wario was riding in his Wario Car with Waluigi who was helping Wario look for some treasure. Wario had gotten his hands on a treasure map from an unknown stranger. He later stopped in front of a cave that the map says to go to. Wario and Waluigi then hop out of the car and enter the cave.
Stage 2: Abandoned Tunnel; Clear the stage. (Playable: Wario, Waluigi)
Soon, Wario and Waluigi find themselves in a room with a treasure chest. They both cheer about being rich until Wario accidentally sets off a trap that not only traps the two in the room, it also causes Coily Rattler, the guardian, to be awakened and to attack the Wario bros.
Fight 2: Vs. Coily Rattler; (Playable: Wario, Waluigi)
After defeating Coily Rattler, the Wario bros continue to steal the treasure, only to see Captain Syrup snatch it up and runs away. Furious, Wario and Waluigi chase after the pirate out of the cave.
In the sky, Kirby was flying past the clouds on his Warp Star, until two laser beams come out of nowhere and narrowly missing him. The Subspace Battleship rises from the clouds and keeps firing lasers. Kirby barely gets hit by one of the lasers and crash lands on the ship. There, he is ambushed by Primid shadow clones and prepares to fight back, until Earthworm Jim crashes into them with his rocket. Then, more shadow clones form and Earthworm Jim and Kirby defends.
Fight 3: Vs. Shadow Primid Army; (Playable: Kirby, Earthworm Jim)
After beating the clones, Kirby and Earthworm Jim share a handshake until both are blown off the ship into the jungle. There, Demille was playing with his yo-yo until a loud crash send him falling on a bush. Earthworm Jim apologizes for the interruption and explains the situation. Demille offers to help and the trio walks through the jungle.
Stage 3: Overgrown Jungle; Clear the stage. (Playable; Demille, Kirby, Earthworm Jim)
While thinking of a plan, Wario and Waluigi drive past the trio with a pile of bananas on the car. Then Donkey Kong and Diddy Kong rush past the trio chasing after the Wario bros. for stealing his bananas. The trio then follow them down a path.
In an unknown facility, Impa had snuck in by crawling in the vents and starts to explore the area as she unsheathed her giant knife.
Stage 4: Security Hallway; Clear the stage. (Playable; Impa)
During her search, Impa stumbles into a room with nothing but a device with a capsule containing the Victory Pokemon, Victini. Victini had somehow got captured and was being tortured by getting her energy sucked up. Impa raised her giant knife and slashed the capsule open, freeing Victini. This however, sounded the alarm and multiple R.O.B's swarmed the room as Impa and Victini prepared for battle.
Fight 4: Vs. R.O.B Army; (Playable: Impa, Victini)
Impa and Victini bust out of the door with guards after them. Meanwhile in another room that looked like a prison, a wall has broken down. The person behind the wall was Shadow Mario who was also breaking in.
Stage 5: Prison Cellar; (Playable: Shadow Mario)
Shadow Mario was now in a hallway and spotted a few R.O.B's going to another room, which he soon follows.
In the sky, Pit is watching an army of Primids invading a castle via fountain. Palutena appears and directs Pit stop the attacks.
Stage 6: Sky Land; Clear the stage. (Playable: Pit)
Pit lands on top of a mountain to find a giant airship that looked like The Subspace Battleship. But before he could react, a purple arrow flies by, narrowly missing Pit. The arrow came from a darker version of Dark Pit and he challenges Pit to a 1 on 1.
Fight 5: Vs. Shadow Dark Pit (Playable: Pit)
Shadow Dark Pit starts to disintegrate into Shadow Bugs. Pit looks surprised and tries to fly to the airship, only to get shot down and fall into a hole in the mountain. In the mountain, Klonoa was warming up near a fire when he see's something fall from the hole far away from him. He grabs his ring and is on pursuit.
Stage 7: Icicle Cavern (Playable: Klonoa)
Klonoa reaches the object which was an unconscious Pit lying in the snow. Klonoa thinks and tries to lift him up, but to no avail. Then he drags him by the wings to take him back to his campsite
Nearby a volcano, Bowser and his minions were walking towards a volcano, Unknowingly to them, Laharl, accompanied by his sister, Sicily, were watching them. Sicily tries to convince Laharl to think of a plan, but already started following them. Sicily facepalms and follows him and Bowser.
Stage 8: Lava Sea (Playable: Laharl, Sicily)
Bowser leads the two into a tunnel. Laharl is curious and looks into it, only to get nearly sniped by a Primid with a Super Scope and an army of Primids, forcing Laharl and Sicily to fight back.
Fight 6: Vs. Shadow Primid Army 2 (Playable: Laharl, Sicily)
After defeating the Primid army, both enter the tunnel, only for Sicily to get kidnapped by Metal Sonic where Laharl chases after him