A/N: This piece is what you get when an overtired author gets weird ideas in her brain, and let's them out of their cages. Apologies.
"What has gotten into you, brother mine?" Sherlock stormed into the Diogenes Club, finally tracking his elusive brother down.
"You," said Mycroft frigidly, "are no brother of mine. Leave."
Sherlock reeled on shock. Things might be tense on occasion between the siblings, but never had Mycroft resorted to such extreme dramatics.
"Alright, let's do it your way," Sherlock said obligingly. "What exactly have I done now for you to disavow our filial relationship?"
"You dare even ask?" Mycroft spat.
"Ohhh, this is going to be one of those days," Sherlock rubbed his temples. "Okay, was it my destroying your favorite, out-of-circulation home film?"
"I've got copies of that one in locations more secure than the American nuclear codes."
"Ruining your precious portraits?"
"I didn't even like them. You gave me the perfect excuse to bin them."
"Err, denigrating your so-called acting skills as Lady Bracknell?"
"I knew, when you praised it, that it was too good to be true."
Sherlock thought hard, and settled on something a little less likely. "Maybe... pointing a gun at you and trying to pull the trigger?"
"Don't be ridiculous! That was only to be expected. Hasn't that kind of thing been happening since Cain and Abel?"
"For Heaven's sake, Mycroft, just tell me!"
"I recieved some intelligence lately... something about a birthday bash. That you actually attended."
"Birth- oh, on my birthday. That stupid thing John dragged me to?"
"You had Miss Hooper, and Mrs. Hudson, and all your little friends."
"But you hate birthdays!"
"Yes. But that cake place, Sherlock! How could you not have sent me a slice of their triple fudge brownies?"
"I'm sorry, brother."
"Apology accepted, pending corrective action, of course."