Paras

Ash and the gang arrived in Mossgreen Village. 
"I want to get some rest and something to eat." Ash said. "Not to mention my Pokemon need rest too."
He had been training with his Pokemon a lot while they traveled.
While traveling they had met a wannabe magician named Melvin. He had two Pokemon, a Exeggcute and Exeggutor. Ash took him on with his Charmander and in the process Charmander evolved into Charmeleon.
At first he was a bit nervous of Charmeleon. He came across stories from the past about Charmeleon becoming disobedient after evolving from Charmander. But when Ash hugged Charmeleon, Charmeleon hugged him back. A indication Charmeleon was still loyal to Ash. And Ash got to know the Pokemon he captured in the Safari Zone better. 
"Apart from food and rest." Brock said. "We need to get more medicine." 
His medicine bag was empty. It wasn't a smart idea for them to travel without any medicine in case of emergency.
After getting food and a nice rest at the village inn, they went to the village pharmacy. The pharmacy was run by a woman named Cassandra and her grandmother.
Brock ended up purchasing medicine from her store.
"I'd like to challenge you to a Pokemon battle." Cassandra said.
"You're on." Ash accepted.
Cassandra's Pokemon was a Paras. Ash smiled at that; he had a Paras as well.
"The reason I want to battle you is to help Paras evolve." Cassandra explained. "You see Paras's mushroom will help me and my medicine if it evolves into Parasect." 
"Absolutely." Ash agreed.
"Let's do it." He said.
Before Ash and Cassandra's battle started, there was a issue. Cassandra's Paras was a coward and weakling. 
"Pika." When Pikachu went to greet Paras, it hid behind her in fear. 
'This will be a challenge.' Ash thought.
"Use a weak Thunder Shock." Ash instructed. 
When Pikachu did so, Paras immediately fainted.
'This is ridiculous.' Ash thought. 'I've seen weak Pokemon before, but this Paras is by far the weakest.'
"Hold on Cassandra." Ash said. "This is getting us nowhere. We need to get your Paras into shape before our battle continues."
"The young man is right." Cassandra's grandmother said. "Your Paras needs to build up it's confidence Cassandra." 
"And I know exactly who can help us." Ash said, holding up a Poke Ball. "Paras I choose you."
Ash's Paras was ready to go.
"Okay Paras we need your help. You see that Paras over there is really weak and needs help. So I need you to help that Paras get into shape." 
Paras nodded.
Ash found some logs and put them in a straight line.
"We will use these logs." He explained. "To test out Paras' attacks."
Misty, Tomo and Brock watched from the sidelines.
"This is a great idea." Brock said. "Sometimes when you're helping a Pokemon, it's best to have a Pokemon of it's own species help out."
"Yeah." Misty agreed it was a good idea as well and so did Tomo.
"Okay Cassandra." Ash said. "We'll have both our Paras use Fury Cutter on the wood."
Ash's Paras' pincer glowed orange and slashed at the wood. Cassandra's Paras did the same, but it wasn't as strong as Ash's Paras. It did take a bit of time, but at last Cassandra's Paras' Fury Cutter attack got strong. They used Scratch on the logs as well. Cassandra was happy that her Paras was doing well.
"There is one attack we should teach your Paras." Ash said. "The move Bug Bite."
Ash's Paras knew Bug Bite, so Ash had her demonstrate it on a log. Paras' teeth glowed white and gnawed at the log. Cassandra's Paras had a go at it too. At first it's teeth wouldn't glow, but after having a go at it ten times, it learned Bug Bite.
After all the tests, it was time for Ash and Cassandra to battle again. They decided to make it a Paras vs Paras battle. Thanks to the training, Cassandra's Paras actually put up a good fight. The Paras were going at each other with their pincers. Then suddenly both Ash's Paras and Cassandra's Paras started to glow and they evolved into Parasect. 
"Wow." Ash gasped. "I wasn't expecting this."
Cassandra was surprised by this as well, but was very happy. She petted her Parasect, while Ash petted his Parasect.
Cassandra was extremely grateful. 
"Ash I can't thank you enough." She said. "And now I can make my medicine." 
"I can tell young man." Cassandra's grandmother said. "That you will be a great Pokemon trainer."
"Thank you." Ash said. Then the gang went on their way.