Work Text:
The song has a sort of simplicity: something easy to sing, easy to play with, easy to build off of. It's something that anyone can sing, no matter how tone deaf or perfect pitch they are.
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It's something that Ford will catch himself singing when thinking.
That John will overhear as he walks past Sherlock at the microscope.
Or Mrs Hudson will notice John humming when he washes the dishes and she's brought up tea.
Violet will read her textbooks aloud to the tune when she'd otherwise fall asleep and has to finish her assignment.
Bonus points if Mycroft or Sally catch Anthea humming it softly while Blackberrying. (Extra points because no one knows where on earth she learned it.)
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Sherlock makes instrumental versions his "family" ringtones: a simple melody violin for Ford, melody guitar for Violet, melody-and-extra-notes for John, super flourishy violin for Mycroft, guitar and violin for Mrs Hudson...
He'll catch Greg whistling it after his phone rings one too many times on a case.
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Greg won't remember where he first heard it, but he'll start making up lyrics to it to narrate his day. Sometimes the tune follows him home and he greets his family by singing their names to it.
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Mary learns it from one of the boys, as they sing Violet to sleep. She later teaches the tune to some of the other people she and Nirupa encounter on their travels.
Sally hums it when she's alone out in the field and almost able to come home.
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Sherlock has a recording on his phone of Ford and Violet almost harmonizing it as they make up more stanzas. It ends in their giggling after a particularly goofy not-rhyme that only eight-year-olds would come up with.
Violet's notebook has a collection of as many verses as she remembers to write down. Ford helps her recall some of the more impromptu/never repeated ones, and come up with more.
When they're older, they get the whole collection of verses printed in a small book for each of their parents.