Trustworthy: The genius detective must have faith in your silence, your belief in his brains, your wakefulness during stakeouts, and your way with a handgun, should he want one used but not desire to fire one himself.
Loyal: Clearly you should prefer him to all other detectives. And the police. And the wife.
Helpful: You’ll indulge your genius detective’s whims without complaint. He’ll badger you for being slow—suck it up. Do the physical labor. Do the washing. Suck on rocks. Above all, two-thirds of the way through any investigation, make a throwaway comment he can ask you to repeat, then use—what an idiot he’d been—to grasp the big mystery’s solution.
Friendly: Your genius detective gets to be rude to clients, not you.
Courteous: See above. However, your genius detective, being asexual, doesn’t mind if courtesy extends to your winking at pretty girls—if it doesn’t interfere with the job.
Kind: Be a shoulder for sobbing clients. Be compassionate when your detective pleads for tolerance about his drug addictions, no matter if you’re a doctor. Be there for him, at all hours, big and dumb. Be his manatee.
Obedient: See above re: manatee.
Cheerful: You might think this is related to “Kind,” but let’s go deeper. Your detective’s life is dark, terrorized. The city crawls with evildoers who want him dead, yet he can’t be who he is without them. He fights crime, therefore he craves crime. You, on the other hand, can be the sun in his life. You show him another way. You symbolize tedium, the ho-hum, the soul of a man who dines alone on vanilla cake: how life would be without crime. Without the need for his talents, without him. Therefore he looks on you as death, but in a friendly way. He mocks you for being dippy, but secretly he wishes he possessed your optimism. He is in love with you, you see, and you might as well be jolly about it.
Thrifty: Who knows how he makes his money, but you’re not getting a nickel. Though there’s always a side career in writing his memoirs.
Brave: Your genius detective is brave because he’s compelled to see the puzzle to the end, even when there’s danger, even when he has to break the law. He’d love for you to feel the same compulsion, but he’s not above the fun of thrill-seeking, so he’ll let you run on that alone. Basically, you’ve got to have big stones, at least bigger than the cops'.
Clean: Actually, this is more a Boy Scout thing. Who cares if a sidekick’s clean? It’s annoying how frequently sidekicks seem to need to eat and sleep, but their appearance and stink aren’t big priorities for the average genius detective.
Reverent: You will be awed by your detective, just like us. Be sure you show it.
For these reasons and more, there was no better sidekick to a genius detective on contemporary British television than David Burke as Watson to Jeremy Brett’s Sherlock Holmes. The other Watson in the series, Edward Hardwicke, was fantastic, but a little too old in the role, and too dry. Burke brings out the boy in Watson and makes him lovable.