This was based off a prompt from r/fanfiction:

'Sour. Perhaps your character has bitten into something that doesn't taste so good, or the actions of another character have left a sour taste in their mouth.'

"I hate this."

Chara withdrew her tongue from her puffy tail. "What do you hate?" she asked.

"I hate this," Chompy said again, gesturing at the box of poffins on a nearby table. "I joined Taurus to learn how to fight, not to sit back and watch contests."

"Not my problem," she replied. She held her head high and smiled at him. "Maybe you're just jealous I'm better at something than you."

Chompy turned away from her with a huff. "Stupid Flareon," he grumbled, "He never should've added her to the team. She's dead weight."

"Hey!" his trainer said. "Chompy?"

The Gabite lifted his head to see Taurus sitting nearby. He groaned at the batch of poffins on the table next to him, which he suspected would all soon be shoved down Chara's gullet.

"Could you do me a favor?" Taurus asked.

Chompy blinked.

"Could you try one of these?" Taurus said, lifting up a tannish pastry. "I need to know if they're the right flavor for Chara."

The Gabite hissed at the poffin thrust before him. He backed away from it.

"I want nothing to do with this," he said, though he knew Taurus wouldn't understand him.

The boy frowned at the snoring Staravia at his feet. "Please?" he asked. "Napoleon and Stark don't want any more, and I just want you to take one bite out of this poffin."

Chompy glared over at Chara.

She perked up immediately and smiled at him.

"Must I?" he asked.

"Poffins taste great," she said. "You won't regret having one."

Taurus held the poffin up to Chompy's face. "Please?" he asked again.

Chompy took the food from his trainer. He stared at him, then at Chara.

Chara slowly nodded.

"Fine," he growled. "I'll do it."

She grinned at him. "Thank you," she said.

Chompy lifted the food into his mouth. He took a big bite out of it, unsure as to what to expect…

His eyes widened. The poffin dropped out of his mouth. His following scream blared as loud as a Loudred's as he spat out what he tasted on to the floor.

Chara screamed at a pitch nearly identical to his. She leaped away from the mess and into Taurus' lap.

"By the thousand arms of Arceus, " she shrieked, "that's disgusting!"

Taurus shrank back. He cringed when people turned to stare at him. "I-I'll clean it up," he said. "Sorry!"

He got a ton of disapproving stares from the onlookers. Thankfully, they all turned around and went on with their business.

Chompy rubbed the insides of his mouth with his claws. "Ith tastesh like lemons," he shouted. "I hateth lemons!"

Napoleon, Taurus' Empoleon, waddled over to his trainer's side. He watched the poor Gabite struggle to remove the taste from his buds.

"Should I," he whispered to Chara, "or shouldn't I?"

Chara stared at him.

"Alright," he said, turning to face Chompy."Sorry about this." Then he launched a Brine attack at his teammate.

Chompy fell instantly to the onslaught of water. He groaned in pain.

"A-at least the taste is gone," he moaned, fainting right then and there.

Taurus sighed and took a great ball from his belt. He recalled Chompy into the ball with a flash of white light.

Chara pulled the case of poffins open with her mouth. She licked her chops.

"Seems sour enough to me," she said. "Let me at them."