AN: I don't own HP.
"Poppy," McGonagall rushed into the hospital wing with tears in her eyes. "It's terrible, absolutely terrible news about Mr Potter."
"What is it?" Poppy fretted, taking Harry and practically throwing him onto one of her beds. Wand already out, and diagnostic charm upon diagnostic charm hitting the boy in the chest.
"HE HAS APHANTASIA!" McGonagall wailed.
"He has what?" Poppy reiterated, taken aback.
"Aphantasia, he can't visualize things in his head! He can't even transfigure a matchstick into a needle," McGonagall whispered, horrified. "He tries the spell and the matchstick just disappears."
"So he needs to go to St Mugos?" Poppy said, getting ready to rush off to the famed hospital.
"It's no use," the usually stern witch bemoaned, "it's not an injury or deformity, there's no cure."
"If there's no cure…" Poppy carefully uttered, "then why is he here?"
"Because he can't do Transfiguration! What is life if there is no Transfiguration?" McGonagall bemoaned.
"This is because he can't do Transfiguration?" Poppy cried out in annoyance. "Transfiguration doesn't matter! Mr Potter, when you're old enough for a girlfriend or wife make sure they have somewhat average Transfiguration abilities for the dozen times a year you'll actually need the skill."
"What do you mean Transfiguration doesn't matter?" McGonagall threatened, pulling out her wand.
"When do you use it? Huh?" Poppy fired back. "Charms and Potions are the backbone of wizarding society, Transfiguration is like the little toe. Absolutely useless!"
"You dare?" McGonagall dropped into a dueling position. "You say throwing a few twigs in a pot or making hair change yellow is more important than Transfiguration? I swear I'll get you," she growled.
"What are you going to do? Make a dog run at me?" Poppy taunted, before lashing out with a bludgeoning hex.