Last time we heard from our Adventure Time friends, they all got their stuff back from the Door Lord, and Lemongrab got-got. PB's 13 again, and this is...
"What Was Unnoticed"... and read the first story in the What Was Series: "What Was Missing".

Previously...

*They stood there for a minute. "I'll see you tomorrow, then," Finn said, turning to leave.
"Wait, Finn!"
"Yeah?"
Princess Bubblegum kissed Finn. "See ya, cutie," and she left.
So Finn walked home.*

Chapter 1- He Lives On
"Hey, man," said Finn, walking in to the living room of his tree fort. Jake was into a video game he was playing on Beemo.
"So," said the dog, not looking up. "Whatcha wonna do today?"
"I think I'll go see Princess Bubblegum, I told her yesterday that I would go see her." The boy said, looking out the window to see the Candy Kingdom.
"Ok, and I'll be here." Jake said almost hypnotized by his game. "Whoo! Water Level!"
"Alright, then." And Finn walked out the door.
Once he walked through the gates, Finn jogged up the steps to the castle's science lab. He knocked on the door.
"Come in!" The princess shouted.
Finn opened the door to see Princess Bubblegum looking through a microscope.
"Hey, Peables." Finn greeted.
PB looked up. "Hi, Finn. Come over here,"
He walked over. "Yeah?"
"I found this algebraic snail. He's, like, really cute... but there's something wrong with him. Do you think he's ill?"
The hero looked closely at the snail. Everything looked alright but... why were his eyes all evil-looking?
"I agree, something is wrong," Finn said.
The snail looked up at the pair and waved.
"Revenge..."
The two looked at each other. "What was that?" They said together.
The same dark voice was heard: "Revenge... Return..."
"Well," said PB, still unsure. "Do you wanna go outside for a walk?"
"Ok." After the snail was in its cage, the two walked out of the lab, not knowing this was the worst spot to be when HE came back...
"Gunter! Gunter, where are you?" shouted an old blue man.
CRASH! Something glass broke in the other room. The Ice King went into the supposedly used gym room, and found a penguin dancing next to a broken bottle, covered in steaming green liquid.
"LOOK WHAT YOU DID, GUNTER!" Ice King shouted.
"Quack,"
"Last time you smashed a bottle I was paralyzed for three days, Gunter. THREE DAYS. Now take your... hmm... pink thing and get out, now. Now, Gunter!"
The evil penguin picked up its pink kitten and waddled away.
"Now that he's out-" the king was interrupted by his pet coming into the room again, without his... kid? I don't know... you know what I mean.
Gunter slapped the Ice King, and ran away. Ice King shouted after him, "GUNTER, IT'S UNNATURAL TO SLAP PEOPLE!" Followed by an angry yell.
"Look, Finn! Oh my grob it's so cute! Look!" Princess Bubblegum bent down to look at something in the grass.
"Oh, holy cow! A candy corn rat," remarked Finn.
The rat looked up at the two and did a flip. It then started running up to the castle.
"Where's it going?" Wondered the princess.
In a split second, the rat came running out from the castle with a test tube in its mouth. It then dropped it in the princess' hands.
"What is it, Poibles?"
"It seems to be the instant antidote to the Freezerburn Flu! But... this was only a theory in my notes, plus I haven't tested it yet."
Finn exclaimed, "Slammacow! This rat knows science!" He picked the rat up. "You should keep her."
"I should, and that's what I'll name her. Science is the perfect name!"
Finn and Princess Bubblegum put Science in a cage next to the snail and went back outside, carefree. Inside the lab though, Science looked nervously at her neighbor. She didn't like him.
And he hated everyone.
Science gulped and tried not to worry as she ran on her wheel. How would she tell the princess about this? What warning does she have?
"Haha, whoo!" Yelled Finn happily as he and Princess Bubblegum ran around tagging each other. The princess jumped on Finn, knocking him down. "You're it!" They both laughed as they lay on their backs on the green grass, looking at the clouds.
"That looks like Jake and Lady Ranicorn," said PB.
"Which cloud?"
"No, Finney, over there!" She pointed at the Cotton Candy Forest.
It was the dog and ranicorn running out of a clearing; they looked like they were in a hurry. "Hey!" Shouted Jake.
The pair got up and ran over to meet their companions. "What's going on?" Asked Finn.
Lady said something in Korean, and gestured over to the Ice Kingdom.
"Huh?"
"She says that we saw something happen in the Ice Kingdom. There was this cloud of green smoke, and then everything went silent. Now this gray fog is covering the land. We couldn't see a thing over there! Not even the palace!" Exclaimed the dog.
All of a sudden, a faint squeak was heard.
"What was that?" Wondered the princess.
"That sounds like Science!" Finn said.
"What?" Jake questioned.
"Our rat, so let's go!" Everyone started for the lab in the castle. When they got up their, Science was pounding on the side of her glass enclosement, and then she pointed to the snail's cage. The cage door was open, and the snail gone. Left behind: a trail of dead science plants, leading out the window, through the now path of dead grass, and toward the Ice Kingdom.