Baker Street Regular

"At this moment there was a loud ring at the bell, and I could hear Mrs. Hudson, our landlady, raising her voice in a wail of expostulation and dismay.

"By heavens, Holmes," I said, half rising, "I believe that they are really after us."

"No, it's not quite so bad as that. It is the unofficial force - the Baker Street irregulars."

As he spoke, there came a swift pattering of naked feet upon the stairs, a clatter of high voices, and in rushed a dozen dirty and ragged little street Arabs. There was some show of discipline among them, despite their tumultuous entry, for they instantly drew up in line and stood facing us with expectant faces. One of their number, taller and older than the others, stood forward with an air of lounging superiority which was very funny in such a disreputable little scarecrow."

- Sherlock Holmes in The Sign of the Four (Doubleday p. 126)

Sometimes, a detective or police officer, no matter how great, simply needs help from time to time. It's no big deal, really. All the greats have at least two partners (You know, since every group should be in three). Usually, their best friend since childhood acts as their assistant. If this is the case, expect to know how their relationship is going to work out, despite the protests otherwise. If it's not, then it is likely an assistant they hired for professional purposes. If it's a woman...well, expect her to put our hero in his place even if he isn't wrong. And well, if it's a guy, expect a couple scenes where that might not matter.

But this is not the page for that, this is the page for the OTHER assistant.

That's right, the Baker Street Regular is that child that finds himself in the situations with the hero, especially the dangerous ones.

Your first run in with the Baker Street Regular is likely while he is searching through the hero's home or office or stealing something to eat because he cannot afford it. If he is not related to the hero in any way, expect him to have no family, except for maybe a sibling or two, but he is almost always the eldest, and almost always male. If he is an orphan, after scratching his back a couple times, expect him to be forever indebted to you and to get you out of a sticky situation in the nick of time, but don't expect him to just leave. You're stuck with him.

After you manage to win the respect of the Baker Street Regular, he will be an invaluable tool and assistant to your group. Life on the street is going to make him able to hear rumors that you won't be able to while you are out on your investigations. He is always good at hiding, especially in situations where the Big Bad is nearby. Expect him to have a slingshot or other projectile weapon to help you out if you need a distraction: He never misses unless the plot demands he does.

If he is an orphan, by the end of the story, more often than not, the detective and his love interest end up his surrogate parents, if not flat out adopting him (and any siblings or close friends he has). Other tropes that you are likely to find a Baker Street Regular on include Parental Abandonment, Troubled but Cute, Just a Kid, and if they are particularly good, Kid Detective.

The Baker Street Regular is a pun on the Trope Namer, the Baker Street Irregulars, who were a network of orphaned street urchins that had been under the employment of Sherlock Holmes to gather rumors, gather clues, and do various odd jobs, in which he made sure to pay what was, to them, an outrageous sum of money for their discretion and loyalty.

Anime and Manga

 * Subverted in Black Butler. Doll, aside from not being the eldest (though that is justified due to her elder "siblings" being Genre Blind), gives Ciel help, covers for him, and fits this trope to a T
 * In Detective Conan, Ayumi, Genta, and Mitsuhiko, the Detective Boys. They're even referred to as Baker Street Regulars in an arc.
 * They literally play this when they entered the Cyberspace Victorian England AU in the Non-Serial Movie Phantom of Baker Street.
 * As the plot approaches the end of Slayers Next, one of these attempts to pickpocket the party, but eventually joins them and befriends Martina. Brilliantly subverted, as

Film

 * Charlie Chaplin in Shanghai Knights.
 * Short Round in Indiana Jones and the Temple of Doom.
 * The street urchin Toto in American Ninja 2, who never forgets to demand money for service rendered.
 * The kid Manco pays to keep tabs on Mortimer in For a Few Dollars More fits the bill.

Literature

 * The Baker Street Irregulars from Sherlock Holmes.
 * Akechi Kogoro had several as well, including Yoshio Kobayashi, who later became famous for something else entirely.
 * Solar Pons has the Praed Street Irregulars.
 * Nobby Nobbs is introduced in Night Watch as one of these. Vimes sees Nobby spying on him for a whole slew of people, and begins paying Nobby to, in turn, spy on them.
 * Sometimes members of the Beggar's Guild, although largely adults and therefore on the very fringes of the trope, act as this for Lord Vetinari as one of many information-gathering channels (it's implied that someone who may in some small way be connected to him spreads rumors that he pays for information, so that they'll come volunteer it to him instead of him needing to send someone looking). It's implied Vimes occasionally gets information from them as well.
 * Ostap Bender from Ilya Ilf and Eugene Petrov's The Twelve Chairs employed them to track one of the titular, possibly treasure-holding chairs.
 * Ben Fischer had apparently started as this in his Backstory in Hell House, before his powers awakened.
 * In the third book of the Bardic Voices series, The Eagle and the Nightingale, Nightingale hires a group of street children to be her eyes and ears.

Newspaper Comics

 * Dick Tracy, Jr, from Dick Tracy is one of the examples of a street urchin who gets adopted. Also appears in the film.
 * Modesty Blaise: Samantha 'Sam' Brown is as East End kid who attends a martial arts class run by Willie. She and her gang of street urchins sometimes fill this role for Willie and Modesty.

Theatre

 * Billy, the page boy to William Gillette's Sherlock Holmes.

Video Games

 * Lilly in Ceville.
 * Luke and, to a lesser extent, Flora in the Professor Layton games are variations on this trope. Flora mostly fits in the sense of being . Luke plays the trope almost straight; however, his parents are still alive and perfectly comfortable financially, and he must . In fact, it's thanks to his parents that Luke is hanging around -- Clark Triton is an old friend of the professor's, which probably explains why they're willing to let a grown man take their preteen son gallivanting off to solve murders impeded by hordes of people who insist you use thirteen coins to spell "waffle".
 * Brynn from Dreamfall acts this way towards April.

Western Animation

 * Kit Cloudkicker in Tale Spin. Molly can also apply in most episodes she's in.