John doesn't want to talk about it.
No one does, really. It's odd enough, that's for sure. It wasn't surprising that Sherlock hated puppies (or was scared of them, as John assumed). No, what came as a shock was when Sherlock arrived home with a newly selected pet.
He came in giddy (if Sherlock could ever be) and sat the cage on the desk. John looked up from his laptop and stared in confusion. "What's this?"
"Our new pet. You said you wanted one."
"I wanted a dog, Sherlock. Not a…what is it?"
"Hedgehog." Sherlock beamed and bent down to look into the cage. The creature ignored him and continued sniffing around his new home. "It's it brilliant, John? Absolutely Brilliant." He moved the creature and held him gently in his arms.
John cleared his throat, doing everything in his power to make sense of it. "You want a hedgehog?"
"I don't want a hedgehog, John, I have one." He shook his head in disappointment. "Marvelous, isn't it?"
John stood and took the hedgehog in his hands, placing him back into his cage. "No, Sherlock, it's not marvelous. Take him back to the store."
Sherlock gave his puppy-dog face, an expression John had only seen once before. He'd come home to find Sherlock creating something in the kitchen that looked like death-rays in action films. Sherlock wouldn't say what it was—simply an experiment—but his face begged John to let him continue. He hadn't.
"If we get a pet, I'll end up being the only one to take care of it." John shut the cage door and sat, doing his best to ignore any pleas. "I could handle that with a dog, but not this rodent."
"But—"
"You'll be bored with it by the end of the week. No."
"It's nocturnal," Sherlock tried. "I'll talk to it instead of you. You can get more sleep."
"You'd have to feed it."
"I will."
"And clean its cage."
"Of course. I'll even fetch, alright?"
"No, Sherlock, hedgehogs don't…" John sighed and turned to his laptop. He typed for a few minutes before standing to grab his coat. "Come on. We're taking it back."
"John—"
"No buts."
"You've given me no reason. Please, John. I'll take care of it. I need something else to keep me entertained."
John sighed and read the words on his laptop screen. Hedgehogs live an average of only four years in domestic homes, but many die sooner from cancer and cardiovascular disease. John had just seen Sherlock's reaction to losing Irene; he didn't want to see him getting attached and lose something all over again.
But he was adamant…and he really, oddly, cared for the thing. He didn't ask for much.
John sighed. "Alright, we can keep it. But one strike and it's gone. Understand?"
Sherlock nodded and looked at his new friend. "What shall we call him? John?"
"I don't know."
"No, I was suggesting it. John. He reminds me of you, oddly enough." Sherlock nodded and decided this to be the best answer. "Yes. John the second."
John—human John—rolled his eyes, hoping Sherlock would grow tired of John II before its funeral.