Yes, I am aware that this is highly illogical. Yes, I am aware that John could never do this IRL. Do I care? Not one whit.
Established Johnlock, only coming in the form of Sherlock trying to grab Naked!John. Rated more for John's wild streak.
Only minimally edited. Too lazy/busy to do a better job. Everyone is probably OOC, but it's pretty crackalicious.
Sherlock was concentrating deeply on his latest experiment when a very displeased Mycroft came storming into the flat, a very happy Anthea and a very happy and very naked John in tow. For once Anthea wasn't on her Blackberry, instead ogling John as she walked.
"Sherlock," Mycroft ground out, "I had rather hoped that John would a good influence on you, but instead I find it is quite the opposite."
Anthea tore her eyes from John long enough to walk over to the table and delicately put John's jumper and jeans on it. Her eyes immediately slid towards her blackberry, and then back to John.
Mycroft harrumphed loudly and Anthea pulled out her blackberry and began to diligently text again. Sherlock had only seen this look on Mycroft's face a few times in his life and accordingly put his experiment to the side to fully concentrate on the bizarre situation in their living room.
John had a large, unrepentant grin. He was also naked, wearing only his socks and his shoes. Sherlock would have hummed in approval, except he could see Anthea peeking over her blackberry and Mycroft was glaring. So he dragged his attention to Mycroft. Mycroft was practically vibrating with anger, something that Sherlock could never remember seeing. He grabbed John by the neck, who was still grinning, and shook him. "Do you know where he was today Sherlock?"
John smoothly broke Mycroft's hold on his neck. "I'd do it again too."
Mycroft harrumped one more time and beckoned Anthea. They descended in haughty silence- at least on Mycroft's part- and John moved to grab his clothes. He avoided Sherlock's grasp neatly and moved towards the stairs. "I'll be down after I've showered. Running through Whitehall and avoiding the guards really works up a sweat."
Sherlock goggled at John. There was no other word for the expression on his face. "Running through Whitehall? Naked?"
John gives him a look. "Well of course. It's really quite obvious- one doesn't need to be a consulting detective to realize that."
"Is that why Mycroft was so huffy?"
"Oh no. He was huffy because I managed to run through the room where the PM was doing his weekly question time. Not even your brother can suppress that."
Sherlock couldn't help it. He began to laugh. "Why were you running naked through Whitehall?"
"Because 1000 pounds was really too good to pass up."
"What?"
"You weren't there that night were you? Drunken bet."
"But you aren't drunk."
"Well it hardly counts if I were drunk at the time of the streaking. And I'll have you know that I just won this month's rent money." John turns and saucily walks up the stairs. "And I don't have to worry about any legal trouble. There are some people even Mycroft can't entirely boss around."
Some fanon says that John knows one of the princes from his Army days. My knowledge of Chicago apartments says that with a discount, 1000 pounds a month could probably cover both halves of the rent.