L9 Crossover Days begins with a crossover with Simien 10.
Lyon, stumbled, lifts his head up, and finds him home. Home, sweet, home. Except he finds an alien that looks like him. "Me?" he asks? The character takes off a mask. "No, it's me." "Spidermonkey? How'd you escape the Oppositrix?" asks Lyon, checking the watch. "Wait, you're on here, and you're out here." "My name is Simien Tumbilly, an Arachnachimp. But just call me Simien." says Simien, who leaps away.
Lyon got up and goes home. He sees himself again, and then says, "Stop imitating me!" he then turns into Opposite Brainstorm, and launches himself into the ground. Himself takes off the mask. It's Simien again. "It's just me," he says. "Well, it needs to not be you!" yells Lyon, who kicks Simien. Simien turns into Acidrain, and the battle is on! Lyon 9 vs. Simien 10.
Simien shapeshifts into a whip, and whips Lyon repeatedly. Lyon turns into Chromastone and blasts Simien. Simien shapeshifts into a trampoline made of goo and bounces it back. Lyon quickly turns into Opposite Chromastone and absorbs it for energy. He then kicks Simien. "Hey, break up the fight, you two!" says a Necrofriggian. "Ic?" "Big Chill?" Simien and Lyon both say at the same time.
Simien puts on his mask and pretends to look in a mirror. Lyon's mom walks toward the inside of the door. "Hide!" all three say at the same time. Lyon turns back to normal and hides his hand in a bush. Ic flies into a tree. Simien can't decide where to hide. Lyon's mom comes outside. "Lyon! I haven't seen you since you were asleep! Come inside and have some dinner."
Simien slowly walks inside and sits down at a table. For dinner, the Niners are having spaghetti and meatballs, mashed potatoes, and spinach. Robert slurps a bunch of spaghetti strings. Jessica dumps the mashed potatoes into her stomach. Mr. Niner stuffs two meatballs into his mouth. Mrs. Niner gobbles up her spinach. Simien slowly picks up his fork, gets some spaghetti and meatballs, and fills his monkey mouth with it.
Outside, Lyon and Ic see Xeenmas in a big drill. Ic calls Zynon, which has a computer. "This computer will tell me how to defeat anything," says Zynon. He types in something with space letters. "Ah, I typed the wrong thing. Let me see if I can find anything," he says. "Big Chill, no. Anthill, no. Aha! Big drill. Turn off power." Well, that should be simple.
Lyon turns into Opposite Big Chill and runs toward Xeenmas' drill. He can't find a power switch, but he finds a lot of cracks. "I have an idea," says Zynon, getting out Due Potenze. He puts Ic's and Lyon's hand in two it, then points it toward the drill. Smoke comes out and causes soil to fill in the cracks. The drill explodes and Xeenmas come flying out.
Xeenmas steals the Chloner and the Nanovaxamech and uses it to make a bunch of giant clones of himself. "Oh no!" yells Lyon. "I remember one of my Necrofriggian friends back on Kylmyys that invented a fusing machine named the Fuso," said Ic. "Except it blew up," he said. Lyon set the Oppositrix to time travel mode. "Let's go!" he said.
Back in the present, Simien was getting ready to get in bed. Mrs. Niner walked into the room. "What's that on your wrist?" asked Mrs. Niner. "The Opposi- I mean, a watch," said Simien. "Where did you buy it from?" "Tammy's Tech Store." "Take it off so I can see it," said Simien. "Hold on," said Simien, hiding under his cover. He turned into Goop and took off the Oppositrix.
Simien got out of the cover and gave the removed copy of the Oppositrix to Mrs. Niner. "Where's the time?" she asked. "It's a standard watch. The first green part stands for 9, the black part stands for 5, and the green part stands for 0," said Simien, staring at Lyon's wall clock. The Oppositrix phased itself onto Mrs. Niner's wrist. "AAAAHHH!" yelled Simien. "What?" asked Mrs. Niner. "Ah, you got it on!" said Simien.
Mrs. Niner twisted it, then pressed it down. She was Chromastone. "What does this mean?" asked Mrs. Niner. "That means that the last two numbers are 5 and 1," said Simien, which kicked Mrs. Niner. Mrs. Niner blasted a beam of energy. "That means that the first number is 9." said Simien. In the past, Lyon, Ic, and Zynon got on the Voiture-Avion and got ready to go into space. Past Robert, Lyon, and Simien were in the area and got on.
Lyon heard the three past people get on and turned around. He saw himself and a warp hole opened up. "It will only go away if something from the present is thrown into it," said Zynon. Ic blasted some ice into it. It closed. "That was easy," said Present Lyon. "Why are you on here?" asked Simien, Present Lyon, Ic, and Zynon at the same time. Two Oppositrixes, one Polytrix, and one Robertrix were smacked at the same time.
"Humongousaur!" yelled Past Lyon. "Crushtacean!" yelled Simien. "Boddarmor!" yelled Robert. "Opposite Humongousaur!" yelled Present Lyon. "All man, I was going for Chromastone!" said Present Lyon. Simien crushed Lyon. Zynon flipped Simien onto his back. "How did you know that was my weakness?" asked Simien. "I read the Ben 10 Fan Fiction Wiki!" said Zynon. "Fourth wall breaker," said Robert.
Ic froze Past Lyon. Past Lyon's tail and hands got out of the ice. Simien turned into Magnetosphere and got in front of Past Lyon. Zynon shot lightning at Simien, but he got out of the way and Past Lyon was blasted out of the ice. Robert shot a boulder at Past Lyon. Back in the present, Mrs. Niner was Goop. "10:10," said Simien. Mrs. Niner turned into Humongousaur. "10:11," said Simien.
"I think it's time to take that off," said Simien, trying to turn Mrs. Niner into Goop. Mrs. Niner grew and knocked down Simien with her tail. "10:12," said Simien. In the past, the Voiture-Avion crashed on Kylmyys. The door opened. Ic's friend Freezer was holding the Fuso. Ic grabbed it and got back in. The jet teleported to the present. The Niners and Simien heard the crash and ran outside.
The door opened. Everyone got out. "AAAAHHH! ALIENS!" screamed Jessica. "Speak for yourself," Mrs. Niner said. Present Robert pretended to faint. Everyone else ran forward to see what was going on. Present Robert turned into Visbile and Present Simien took off his mask. Present Simien turned into Arachnophobia and tied up Jessica, Mrs. Niner, and Mr. Niner. He flew them to the other side of the house.
"We should be focusing on what's important," said Present Lyon, pointing to the giant Xeenmases. Everyone got in both the past and present Voiture-Avions. Ic put the Fuso onto his Voiture-Avion. A portal opened. Both Voiture-Avions drove into the portal. A gigantic alien named Pastpresent came out of the other side. He turned invisible and snuck behind a Xeenmas.
Pastpresent turned visible and threw the Xeenmas at others. Those disappeared. Pastpresent shot boulders at different Xeenmases. That one disappeared. Soon, there was only one Xeenmas left. He picked up the Nanovaxamech and used it to make him grow to the size of Pastpresent. It also gave him lasers. Pastpresent magnetized a building above Xeenmas and dropped it on him. The fight was on.
Xeenmas picked up the building and used it as a weapon. He whacked Pastpresent. Pastpresent turned intangible and popped out behind Xeenmas. He froze him and knocked him down. Xeenmas broke out and shot a laser at Pastpresent. Pastpresent shot lightning. The two blasts combined and turned Pastpresent and Xeenmas to normal.
The blast caused a wave that sent the pasts to the past. It also wiped Jessica, Mr. Niner, and Mrs. Niner's memory. The copy of the Oppositrix got sucked into Simien's ID mask. "It was nice working with you guys," said Lyon. "Don't mention it. You can have the Fuso," said Ic. "So, what aliens were used in the past?" asked Simien. "What aliens were used in the present?" asked Lyon. After telling, everyone fainted.
- Opposite Brainstorm
- Opposite Chromastone
- Big Chill
- Opposite Big Chill
- Opposite Humongousaur
Simien with ID Mask