Written for the LiveJournal community Watsons_Woes for their July Writing Prompts challenge. The prompt for day 23 was: Earworm. We've all had music get stuck in our heads. Now do the same to a character in your story.
The song I imagined was The Major-General's Song from Pirates of Penzance (though technically the 1888 production of Pirates closed in June and Watson didn't meet Mary until later that year).
_Persistence of Music_
After I went to a Gilbert and Sullivan show with Miss Morstan, I returned to Baker Street happily humming. I woke the following morning with the refrain of one song still in my thoughts, where it persisted all day. I thought nothing of it until Holmes threw down his paper and snapped, "Really, Watson, would you cease that infernal humming?"
"I'm sorry, I didn't realize," I said apologetically.
A little while later I noticed that the tune I was hearing in my head was being repeated. Holmes had begun humming the notes plaguing my thoughts despite never seeing the musical.