Okay, this time you can consider this either a ficlet or a triple drabble. It.... got away from me.
“You know of Harry of course,” said Dr John Watson, “But this is my younger sister Dawn. Dawn, this is Sherlock Holmes.”
Dawn waved nervously. “Um, hello Sherlock?”
Sherlock glanced fleetingly at her, grunted once and immediately returned his attention to studying everyone else in the pub. “Adopted, one assumes. In as much as that is the only way you can have a mystical ball of energy as your sister.”
Watson’s jaw dropped. “I... what... Sherlock!”
Sherlock sighed loudly. “Come now, John. Her height, her posture, the colour of her eyes all indicate a very different genetic heritage. The general demeanor of her hands and their positioning indicate a practised kleptomanic, who I would say, has been caught at least once in the act.”
Watson shot one look at the now blushing Dawn. “We will
talk about that particular deduction later,” he said, before returning his full attention to Holmes. “What other possible reasons could you have for imagining my baby sister to be not even human?”
“I was young!”
“Well,” Holmes said consideringly, “There’s always the bright green glow, of course.”
“I was impressionable and easily led astray!”
“No, you weren’t,” said Holmes and Watson together.
Dawn pouted. “I could have been,” she said sulkily, and folded her arms in a strop.
Watson buried his face in his palm for a moment. “Give me strength,” came his muffled voice. He took a deep breath, sat up and faced Holmes. “So, mystical ball of energy. Is that the first thing that came into your head? Why not go the whole hog and claim she’s a clone, created by some sort of alien race?”
Sherlock frowned. “Don’t be ridiculous, John,” he said, “Obviously, that would be the American exchange student over there.”
At the bar, Jon O’Neill choked on his pint.