Towards Effective Tail-Chasing (PG; Hermione, Crookshanks, Argus, Severus; 700 words): Argus knows a thing or two about mongrels.
Hermione was in the staff room watching Crookshanks half-heartedly chasing his tail over the remains of a catnip toy and otherwise pretending to read until he showed up when two things happened at once: the door opened, and Crookshanks abruptly sicked up.
"What's up with yer half-breed?"
"Good evening, Mr Filch," Hermione said, with pointed politesse, as she spelled away the remains of Crookshanks’ hairball. "Come here, Crooks."
Crookshanks ignored her and wandered over to Filch, rubbing against his legs.
"But it's not a good evening, is it?" Filch asked, bending down with some difficulty to pet Crookshanks. "You've been giving this mongrel catnip. Yes, she has," he continued, speaking to Crookshanks, "even though a witch ought to know better.”
Hermione crossed her arms in annoyance. "What do you mean by that?"
Filch straightened up with a groan, bringing Crookshanks with him. "There's a good boy. Kneazles often develop an allergy to catnip as they grow older."
"They do? How do you know?"
"I can read, can't I, woman?"
Headmaster Snape entered the room. "Argus, Professor Granger is obviously a woman—"
"—but you needn't address her as if she were a young one."
Filch slowly turned to Hermione. "I'm ever so apologetic, Professor Granger—but you should know better. Ain’t you ever read Care and Feeding of Kneazles?"
"No," Hermione replied simply, trying not to let her irritation with Filch show in front of Snape. "Perhaps I might borrow your copy?"
Filch snorted. "Don't usually lend my books."
Snape cleared his throat.
"But I suppose I wouldn't mind, for this one’s sake," Filch continued, nuzzling Crookshanks' head with his cheek.
Crookshanks purred loudly, and as usual, Hermione couldn't believe how well he got on with Filch. "Thank you. I'd appreciate that."
"Yes, well, yer mongrel would appreciate some stomach tonic. I've still got some from when . . . I've still got some."
Hermione's irritation lessened as Filch's eyes grew watery. "Perhaps you wouldn't mind giving Crooks a dose now? I could come collect him and that book from your office later. That is, if you wouldn't mind?"
Filch scowled, but his posture slackened. "Always happy to be of service," he said, before stalking off.
"That was . . . nice of you, Professor Granger."
Hermione wanted to reply in kind, but she found herself saying, "I didn't need you to 'rescue' me from Mr Filch, Headmaster."
Snape turned from the teapot and swept his gaze over her, bristling like an offended cat. "No, of course you didn't. I'll just leave you to your reading."
"Wait, please. I didn't mean that I wasn't grateful."
"Then what did you mean?"
"I meant, er, oh, I’ve been wanting to ask you about Mr Filch."
Snape snorted. "Have you."
"Do you think he's ready for another cat?"
Snape sat down at the table, and Hermione joined him.
"I didn't think you liked Argus."
"Crooks likes him."
"Perhaps Argus would, but you'd have to persuade Irma to allow it. She doesn't care for cats."
Hermione smiled. "Cat fur on books is difficult to dust. . . . Have you ever read Care and Feeding of Kneazles?”
“No, I’ve never had a pet.”
“You’ve never had a pet? That’s sad.”
“Most people would assume that the pets I haven’t had were better off,” Snape replied, watching her above the rim of his teacup as he took a long sip.
Hermione flushed more deeply and launched into a discussion of all the reasons why he should consider being owned by a pet.
Meanwhile, Argus was enjoying a Muggle mystery novel while Crookshanks licked the remains of a tonic-laden treat from his fingers.
“There’s a good boy. Think Snape will make any progress tonight?”
“Mreow,” Crookshanks replied, turning in Argus’ lap and beginning to wash himself.
Argus chuckled. “Me, either, but don’t worry: when he finally does catch yer mistress’ tail, you can always spend the nights with me.”
Crookshanks left off lapping at his fur. “Mrrerpht?”
“Don’t worry none about Irma. A worse woman for readin’ I never met, and she only takes books to bed with her at night. Just keep yer distance in the afternoons, understand?”
Purr, purr, purr.
“Good mongrel,” said Argus, turning back to his book.