This imagination's began on dialogue in s2e1! They played the clue game.
It's too hard to translate... sorry In summary, Sherlock jabbering on endlessly, ignoring the game rules. He fingered John as the suspect. and John's patience is being tested.
S: The criminal is an army doctor, recently retired from his post in Afghanistan! The reason he doesn’t take his hands out of his pockets is because he still has gunpowder left on his sleeve. He must have a strong moral principal. Blah, blah blah… ….John…? Why aren’t you exclaiming “Brilliant!”?
W: NO, no, no, no, no, no…! Do you even know the rules? Anyway, if you were right, this bloody sociopath with the harpoon is going to be beaten to death by that army doctor.