This is my first fanfic - just a silly idea I finally wrote down. Hope you enjoy it.

Disclaimer: characters aren't mine.

"John, what is this?" Sherlock was sitting on the couch, elbows on his knees, steepled fingers resting against pursed lips.

"Um… a cat, Sherlock?"

"Yes, I know it's a cat! Don't be so obvious!"

The feline in question posed magnificently on the coffee table, with his tail curled sedately around his feet, and regarded the world's only consulting detective with an inscrutable expression. John smiled. The cat had adopted Mrs. Hudson earlier this week and their good-hearted landlady had taken him in. He already displayed a decidedly proprietary air regarding 221 Baker Street and its contents.

Sherlock returned the gaze steadily. As John watched, the detective's eyes narrowed almost imperceptibly, intent on the furry enigma before him. The cat's regard continued, unblinking.

"Excuse me. Are you having a staring contest with a cat?"

"What? No! Of course not!" Sherlock muttered even as he continued to meet the serene emerald eyes.

The tip of the grey tail flipped once and the cat abruptly yawned, exposing perfect – sharp – white teeth in a feral grin.

"Mrrff," he pronounced. Stretching languidly, the cat flowed from the coffee table to the floor and disappeared out the open doorway (which John had left ajar).

Sherlock looked to John, perplexed. "What was that?"

The doctor chuckled. The cat had inspected him yesterday. "You passed the test."

"Test?"

John couldn't resist. He grinned. "You just had a CAT scan."

I take no credit for the bad pun, but I couldn't resist putting it in... Thank you for reading. Constructive comments are very welcome.