"You brought a feline?" Sheldon demanded. "Into this apartment?"
"I... I looked through the contracts," Leonard replied, being brave. "And yes, yes I did. I bought a cat."
Sheldon blinked, running though the sections and paragraphs in his mind. Interestingly, none of them forbade cats – although he was sure there was some sort of subsection regarding animal hairs.
"Make sure it stays off my spot," he ended up saying, then darted off.
Leonard pulled a face, uncertain of this apparent victory over Sheldon's tyranny, but dismissed it and turned to the basket in his arms.
"I think I'm going to call you Louis," he stated, more to himself than anybody else, and sauntered into the bathroom to set up some cat litter.

-----

Knock-knock-knock. "B'enny." Sniff.
Knock-knock-knock. "B'enny."Sniff.
Knock-knock-knock. "B'enny." Sneeze.
Pause.
Knock-knock-knock. "B'en –"
"What?"
It was three in the morning. Sheldon stood in the hall, dressed in his Wednesday pyjamas, even though it was Tuesday. His eyes were bloodshot, and from his hand dangled a ridiculously large handkerchief.
Penny's eyes widened in surprise. She instantly forgot the time and ushered him inside.
"Sweetie, what's wrong? Where are your proper pyjamas?" she exclaimed, dashing to her kitchenette to find the Sheldon-approved snacks she kept on hand to shut him up (not unlike Scooby Snacks).
"B'enny," Sheldon began, "B'enny, Ennad bought a bat."
Penny paused. "A bat?"
"A bat," Sheldon repeated, unaware of his speech impediment. "A banky, ebil, crool sbesiman of the febine kind."
Penny took a moment, but carefully translated the sentence.
"A manky, evil, cruel specimen of the... feline kind?" she repeated uncertainly.
"B'yes." Sniff.
A lightblub switched on in Penny's head.
"And you're allergic? Oh, sweetie, that's terrible!"
"I boe." He paused, as if in consideration, then launched into an undecipherable torrent of snot and orders.
"Slow down, Moon Pie," Penny sighed, all sympathy long gone. "You want me to kill Leonard's cat?"
"Bust disbose ob it," he corrected. "It bustn't bave to bie."
She rubbed at her eyes, suddenly aware of how tired she was. She'd worked a long shift and she had another to match tomorrow – no, today.
"Listen, you can sleep in my bed. I'll talk to Leonard tomorrow morning," she offered, already regretting an uncomfortable night ahead.
"Bokay," Sheldon sighed, and trotted off to Penny's room.
"Never fails to amaze me," Penny muttered, searching for a pillow as Sheldon flicked off the lights.

----

As it was, Penny wasn't able to catch Leonard that morning, and had to put up with a whole day of "Penny? It's the phone for you... again." By the time she finished her shift, she was ready to kill that cat with her bare hands.
"Leonard! I need to talk to you!" she screeched, bursting into the apartment. "It's about that –"
She froze. Leonard, with the glow of a new parent, was showing off a tiny ball of grey fur to Wolowitz and Koothrappali. No sleazy remarks greeted her. Instead, the nerd boys were acting like the most loyal members of a mothers' club.
In comparison, Sheldon was skulking in a corner, deliberately avoiding his seat because of its cat proximity. He looked furious.
"Penny!" Leonard said, oblivious to Sheldon. "Have you met Louie?"
The desire for blood instantly left Penny's mind as she stooped to pet the fuzzball.
"Hello, sweetie! Who's a good kitty? You're a good kitty! Meow, meow!"
Sheldon began an indignant snort that ended in a sneezing fit. He was ignored.
"Oh, Leonard, he's gorgeous!" Penny gushed. "Can I hold him?"
Leonard gently passed the kitten to his neighbour, who was so enraptured she ignored Wolowitz's comment, "I wish I was that cat."
"B'enny!" Sheldon called from his corner, miserable. "B'enny, bake the bat go abay!"
"Shh," she replied absentmindedly.
There was no hope now.

----
Knock-knock-knock. "B'enny." Sneeze.
Knock-knock-knock. "B'enny."Sneeze.
Knock-knock-knock. "B'enny." Sneeze fit.
Pause.
More sneezing.
"B'enny!"
Penny slowly opened her door. Sheldon hadn't even bothered with proper pyjamas tonight – he was in what looked suspiciously like bathers and a rash vest.
"Do you want to escape Louie again?" she asked in a heavy voice.
It wasn't the first time this week. In fact, Sheldon had turned up at 3 every night since Louis the cat had been introduced. It was putting a strain on Penny's already dangerous temper, and that was never a good thing.
On the other hand, the sheer adorableness that was Louie seemed to be throwing it back in balance, so maybe things could work out.
As usual, Penny made a bed for herself as Sheldon got himself settled. Half an hour of sniffles and moaning had elapsed before Penny had an idea. She crept slowly off the couch and into her room, where Sheldon was staring at the ceiling.
"I know how to make you sleep, sweetie," she whispered.
Sheldon, naturally, didn't pick up on her evil tone, and nodded enthusiastically.
"It's worked before," she added. "I think it'll work very well."
"Bo on."
She took a breath, then began to sing, very softly, "Warm kitty, soft kitty, little ball of fur..."

----

It was when Leonard found Sheldon as he stole Penny's mail, sleeping in the foyer with a scowl, that he decided a cat might not be the best idea if he wanted to stay neighbours with her.

AN: Ok, kudos if you can tell me where the name for Leonard's cat came from... come on, guys.