Sherlock had that look on his face.
The 'I-think-you'll-consider-this-Bit Not Good-but-perhaps-you-won't-notice-if-I-don't-say-anything' look.
This look was normally followed by yelling, cursing and, on one memorable occasion, quite a bit of laughing.
John had entered the room from a walk through the park and was standing in the living room. He had originally been heading to his room but had paused to glance at his flatmate, who was currently standing very calmly on top of the coffee table, with a box riddled with holes in his hand.
That's not a sight you see everyday.
"Ah, John. There you are."
There was a rather awkward silence as John tried (and failed) to comprehend what Sherlock could possible be doing.
"Yeah...um...what are you doing Sherlock?"
Suddenly, Sherlock stiffened and slowly raised the box.
"John. I want you to stay very, very still."
His hair itched. He went to scratch his head, but he was reprimanded almost immediately by Sherlock.
"No! Don't move. We don't want to kill such an unusually large specimen, now do we?"
At the word specimen John had started to panic.
Now that his head seemed to have become hypersensitive, he could feel hairy, fat legs moving over his hair and when they touched the skin on the side of his face he let out a very manly screech.
"WHAT IS ON MY FACE!"
He rolled his eyes.
Sherlock Bleeding Holmes had the nerve to roll his eyes when there was...something...crawling its way along the right side of his face.
"Its a Bird-eating Spider, John. It dropped off of the ceiling when you walked into the room. And if you could please stop speaking, it would be greatly appreciated."
By this time the spider had started to creep its way down John's neck, so John did the only thing he really could.
He momentarily experienced the need to shut down his brain.
He most certainly did not faint.
Bird eating spiders look so...hairy. And large. Ugh! Look them up. Poor John, hate to have one on my face :)