Kid Sidekick

A muscle-bound, gun-toting Badass. And his (rather competent) kids.

A character, often an adult or sometimes teenager, has a considerably younger Sidekick. Traditionally the kid will often act as The Watson for the main character, and/or as someone for younger audiences to identify with. Sometimes the kid acts as a Morality Pet or as a Wish Fulfillment personification, which goes some way to explaining the implausibility of a responsible adult putting a young child in dangerous situations. Sometimes the sidekick will be a Teen Genius (or younger) in an attempt to justify their presence, or even a Cute Bruiser. Other times, they're The Load and a Damsel in Distress.

Compare Tagalong Kid, Kid Appeal Character, Bratty Half-Pint and Baker Street Regular. Contrast Older Sidekick.

Examples of Kid Sidekick include:

Anime and Manga

Jim Hawking in Outlaw Star.
Radical Edward of Cowboy Bebop.
Lone Wolf and Cub is the epitome of this trope. Ogami Ittou's sidekick is three years young.
Lirio from El Cazador is a loli sidekick to Badass Normal Ricardo.
Hayate's partner, Reinforce Zwei in Magical Girl Lyrical Nanoha. Her non-Fun Size form looks around ten, with her actual age being younger.
Lin and Bat in Fist of the North Star.
Wendy Garret of Gun X Sword is a teenage example of this. She very rarely helps out in battle, but she's better at thinking than Van is. She functions as a manager, handling the money and making travel arrangements.
Eve of Black Cat is one, but she hardly has trouble keeping up.

Comic Books

Robin, sidekick of Batman, is the Ur Example, and is retained in almost every incarnation of Batman, no matter how Darker and Edgier, simply because of tradition. (notable exception in the Dark Knight Trilogy)
- Subversion: the makers of the new Batman movies have stated emphatically that Robin will not be included. They Handwaved this with stuff about him still being a kid, but we know it's actually about wanting to stay Darker and Edgier and not get 60s-style campy.
  - Nolan has gone on record to say that at this point in Batman's life, Robin would probably have to be played by someone like Frankie Munez, which is a pretty good explanation for why he isn't in the recent movies.
- He's also stated that at this point in Batman's life Dick Grayson is most likely still sleeping in a crib.
Step forward Rick Jones. For decades Rick has been Marvel Comics' stock sidekick. He has been partners with The Hulk, Captain America (comics), two Captains Marvel, and ROM Spaceknight. Must be some kind of record.
Following the Batman formula, other younger sidekicks to adult superheroes include Supergirl, Speedy to Green Arrow, and Wolverine's various sidekicks, usually of the young girl type. (Kitty Pryde, Rogue, X-23, Jubilee)
- Also on the sidekick squad: Aqualad to Aquaman. Kid Flash to Flash.
- Wonder Girl, Spoiler, Flamebird (or not).
DC thrives under this trope. Darkly parodied with Kid Devil, whose adult counterpart and idol Blue Devil was barely aware of his existence, despite having made a Deal with the Devil to be a Superhero with him.
The Clock, a very first Golden Age hero (last seen in 1944) and his kid sidekick Butch (a girl). Butch, incidentally, originally wanted to be the Clock's "moll", much to the hero's mortification. She eventually got over it.
Johnny Bates, AKA Kid Miracleman, from the comic Miracleman. (Originally known in the UK as Kid Marvelman and Marvelman.) Alan Moore's 1980s revival of the series not only aged the character to adulthood but gave him one of the most horrific Face Heel Turns in comic book history.
The Silver Age-inspired Freedom Force computer games give us Liberty Lad, sidekick to Super Patriot The Minuteman. Young Nick Craft, founder and president of the Freedom Force Fan Club, tags along after the team as they try to bring down mobster-turned-supervillain Pinstripe. Naturally, he gets shot.

Pinstripe: Now youse gotsta choose, heroes. Come afta me, or save da brat! Mentor reports that he needs an immediate transfusion... or he'll die! Minuteman, feeling responsible for the plucky youngster, valiantly volunteers to give his own blood to the boy. Mentor warns him that they have no idea what will happen, because Minuteman's blood is infused with... Energy X.
'Minuteman: By the Constitution, Mentor, there's no time! The Energy X in Minuteman's blood gives Liberty Lad super strength and agililty and a penchant for red, white and blue tights. He's one of the more fun and effective characters in the game.

- And from the same game, we have Man-O-War and his preteen sidekick, The Sea Urchin.
Bucky Barnes was this to Captain America (comics) in World War II. On the Invaders as well was the first Human Torch, who had sidekick Toro, with near identical powers.
Oddly enough, Moon Knight had an adult sidekick (or at least young adult) who was temporarily killed off and rebuilt as an evil cyborg named Midnight.
German detective Nick Knatterton had Toni Knatter, in one story. The Meaningful Name was Lampshaded by our hero.
Spider-Man started as a deliberate subversion of this trope. Stan Lee had grown sick of teen sidekicks, so he decided to create a series that featured a teenager as the main star, rather than as support to an adult hero. Everyone thought that It Will Never Catch On...but it did.

Film

Kenny from Gamera
Short Round from Indiana Jones and the Temple of Doom.
Last Action Hero even has the Kid Sidekick refer to himself as the 'Comedy Sidekick', which should be a sub-trope of sidekick.
The Jedi in Star Wars pair up young padawans with older Jedi to teach them the way of the force. The difference here is that they often remain padawans into their twenties, making them former Kid Sidekicks by that age. They are usually Knighted after that, and soon begin the cycle again by choosing their own padawan. Generally padawans and their masters are sent on diplomatic missions, but with the way the Star Wars universe works, and with the advent of the Clone Wars, it's almost a given that the padawan will be forced to fight.
Lex and Tim Murphy from Jurassic Park.
Mindy Macready/Hit-Girl from Kick-Ass.

Literature

Patsy Murphy and Chick in John R. Coryell's Nick Carter.
The Red Lama and Kim in Rudyard Kipling's Kim. Interestingly Kim is The Sidekick to several different characters including the Red Lama, Mahbub Ali, and so on as well as being The Hero.
Doc Wilde, a Doc Savage parody, has his two kids who he's been raising to be badasses like himself come up with him on his adventures.
In Wearing the Cape, Hope (18 years old) becomes Atlas' sidekick in order to learn the butt-kicking ways of Atlas-type heroes. The whole mentor/sidekick angle is played up for the media (her costume is even color-coordinated to match his), but it's clearly understood to be a temporary arrangement, more like an apprenticeship.

Live Action TV

Mark Hollander to the titular Ace Lightning (albeit sometimes reluctantly).
Rather bizarrely on Heroes, Sylar temporarily gained one of these in the form of Luke, a troubled teen with the inexplicable desire to go on a road trip with a super-powered serial killer. And keep annoying him. His survival is something of a miracle. The series strongly implied at the time that Luke is Sylar's brother. As with most things on the show, this turns out to not have been the case when it's later learned that Sylar is a Petrelli.
In Nickelodeon's U-Pick Live segment, they held a contest where the winner would be added to the show as Pick Boy's new sidekick. Something must have gone wrong backstage though, because no kid was ever brought in.

Newspaper Comics

Junior (possibly Henry Steele, Jr.) in Dick Tracy

Tabletop Games

A feat in Mutants and Masterminds lets you have one (who can be any of the Sidekick tropes, but guess which one is most common except among obsessive powergamers). There are also a few in the Freedom City setting, most notably Arrow (Speedy to the Bowman's Green Arrow, in several incarnations).

Video Games

Subverted in Chrono Crusade with Chrono and Rosette. Chrono looks like (and sometimes acts like) a twelve-year-old, but it's soon revealed that he's really a demon that's probably at least a century old, making him actually Rosette's Older Sidekick. Also played somewhat straight with Azmaria, a 12-year-old apprentice in the Order who is assigned to work with Chrono and Rosette.
Henry Hatsworth in the Puzzling Adventure: Cole, for Henry Hatsworth. He's later revealed to be a "Well Done, Son" Guy and in actuality the Big Bad in disguise.
Kirby: Sword and Blade to Metaknight.
Maya Fey, the main assistant in the Phoenix Wright Ace Attorney games may or may not count, as she starts 17 but becomes 19 by Trials and Tribulations, although she tends to act like a little kid sometimes. Phoenix also had Ema Skye in one case when she was 16, and Apollo Justice has Trucy, who is 15.
- 8-years-old Pearl Fey may also count in the missions where she plays a sidekick to Phoenix.
- It's tradition for the protagonist of the Ace Attorney games to have a cute young girl for a sidekick. Or Gumshoe. Even Edgeworth teams up with Kay Faraday... and then it gets sent up when he's helped by Franziska Von Karma. (who also briefly and hilariously becomes Phoenix's sidekick in the third game)
Miles 'Tails' Prower, sidekick of Sonic the Hedgehog, is of the Gadgeteer Genius variety and has abilities that complement Sonic's. Later games introduced Cream the Rabbit (who has her own Sidekick, the Chao named Cheese), who serves as more or less the female counterpart to Tails (hence why they are often shipped together, despite almost never interacting). She started as a sidekick to Amy, but in Sonic Rush she acted in this capacity to Blaze. In Sonic Rush Adventure, Blaze gets her own sidekick in Marine the Raccoon.
Professor Layton gets Luke. Flora may also count.

Web Comics

Gordito Delgado from The Adventures of Dr. McNinja. The Doctor even compares himself to Batman when he decides to take Gordito in. Of course, the Doctor compares himself to Batman regardless. Note that Gordito's origins - a child of a family of circus performers who was orphaned mid-show - is a tribute to Dick Grayson's.
Nip and Tuck has an arc that shows a Serenity-inspired movie featuring a kid sidekick.
Alamand to Soli of The Meek.
Sunspot to Stardust in Attack of the Super Wizards.
In The Adventures of Gyno Star, Gyno-Star's sidekick is a teenager named Little Sappho.

Web Original

From the Global Guardians PBEM Universe, Golden Age hero Barnstormer was always accompanied by his Kid Sidekick Tailgunner.
In the Backstory of the Whateley Universe, the pre-World War II superhero Champion had two: Miss Champion and Champion Junior. In a Shout-Out to the way heroes age in Comic Books, Miss Champion only aged (from then on) at about one-fourth normal, which really messed up her social life. Miss Champion is still around, and one of the important side characters of the universe.

Western Animation

In The Fairly Oddparents, The Crimson Chin's sidekick, Cleft the Boy Chin Wonder, is a ten-year older. Makes sense, because his alter ego is actually no other than Timmy Turner himself.
Jade from Jackie Chan Adventures.
Spoofed with Barnacle Boy, Mermaid Man's sidekick on SpongeBob SquarePants, who is still treated as a child even though both of them are now old men. One episode has him doing a Face Heel Turn because of it.
Jan and Jace, for Space Ghost.
Spinner (and his dog Paddlefoot) of Clutch Cargo.
And the Wonder Twins probably count, in Superfriends.
The Transformers have a bad habit of dragging young humans into their battles - young humans who tend to have no powers or skills that make letting them within a mile of Decepticons anything less than criminal negligence. Giving them a reason to be around at all is relatively new to the franchise.
Young Justice has the main characters being sidekicks to members of the Justice League (Robin to Batman, Aqualad to Aquaman, Kid Flash to The Flash and Speedy/Red Arrow to Green Arrow).
The Cadets in Voltron Force are a fairly good example. They bring considerable talents to the team - Vince's Technopathy, Larmina's martial arts talent and Daniel's piloting skills and agility (both physical and mental) complement, rather than overshadowing, the rest of the Voltron Force.