John Watson, well. John Watson has his jumpers. And like John Watson, those jumpers are soft, warm and rather cuddly. Both of them are practical, dependable, not all that fashionable and sadly a little bit beige.

In some aspects of life, John Watson and his jumpers are possibly interchangeable. For example, as a replacement for the missing skull Sherlock would surely not notice the difference between John and some wool. And when Sherlock once again demands John's attention, assistance or tea-making skills the jumper would be just as good at ignoring the demands as John is. And the jumper would definitely be just as competent at not replying to Mycroft's texts.

However, there are things the multi-talented John Watson can do that his multi-talented jumpers cannot. The ability to walk, for example, is useful in making sure Sherlock isn't causing mayhem at crime scenes; and in the same situation his powers of speech are good diffusers of tension. His jumpers are also yet to develop opposable thumbs and the ability to use a computer, and without those skills there isn't much chance of being a doctor.

Then there's John Watson's bravery, courage, morality, and most importantly his ability to pull a trigger. The jumpers lack these skills, and as such it is probably a good thing that John Watson does exist as an actual human being.

Sherlock Holmes, he has his coat. Like Sherlock Holmes, the coat is expensive, deceptively strong and heavy, and a showboat. They are both ridiculously long and sleek, unsuitable for most social situations, painfully – and almost incidentally – stylish, and very beautiful.

There are some situations where Sherlock Holmes would not be missed if his coat were to suddenly take his place. Lestrade would surely shed no tears if in the middle of a sarcastic deconstruction of his team's skills (or lack thereof) Sherlock were to be replaced by some wool mix. Certainly when making a dramatic entrance or exit the coat was already taking the limelight; Sherlock's presence wasn't really needed. The coat also probably has better social skills than Sherlock himself, and in most situations its lack of the powers of speech would be a welcome change. The coat would also live politely with John without any chance of heads, eyeballs or fingers appearing in their kitchen appliances.

Of course, Sherlock Holmes has a multitude of skills that his coats are yet to exhibit. His often useful acting skills, for one example, are a long way from being paralleled by the wool. The coat also doesn't share Sherlock's sharp wit and turn of phrase. And, lacking opposable thumbs and a chin, the coat is unable to play the violin, leaving John with nothing to entertain him when the TV is boring. Plus, who would eloquently reply 'fuck off' to all of Mycroft's texts to both Sherlock and John.

And then there are Sherlock Holmes' deductive powers. His ability to get up everyone's nose and inside their brain, solve crimes and (most importantly) scare the bejesus out of new acquaintances are yet to be rivalled by the coat. And seeing as those powers have saved lives, apprehended murderers and pissed off Anderson, it's probably lucky for everyone that Sherlock is yet to be rendered obsolete by the coat.

Mycroft Holmes, well, he of course has his umbrella. Like Mycroft Holmes, it's long – yet not exactly streamlined – pointed, and smooth. They are powerful, useful, protective, and will both have your eye out if you stand too close in a storm.

There are not many situations where Mycroft could be replaced by his umbrella, if the truth is told, but he is not entirely indispensable. The umbrella could more than replicate his lack of enthusiasm for god-awful government events and following silent sulk. And the umbrella may have more chance of making Sherlock act like an adult human being during Mycroft's visits to Baker Street. John Watson may also have been more inclined to tell the umbrella about Sherlock's exploits and ease the surveillance process.

Overall, though, Mycroft is not expendable for replacement by an umbrella. His department's movements and co-ordination would surely not be as controlled and undetectable under the orders of an umbrella. The umbrella would also be unable to tease his brother mercilessly about his crush on John Watson, a public service as far as Mycroft is concerned. And also, while the umbrella may be capable – with some assistance – of protecting Sherlock and John from rain, sleet, snow and hail, it would likely be unable to fend off a murderous psychopath and make sure they can pay their rent.

Most importantly, though, the umbrella lacks the motor skills needed to gain information by jamming itself into people's ribs. Mycroft, in turn, lacks the sharp point that makes this action so effective. Without this joint action, the British Government would certainly not run as smoothly, so it is probably in the country's best interest that they do exist as a team.