Little Miss Con Artist

"Penny: I'm a thief!

Finn: But you're just a cute little girl!

Penny: And.... I'M A THIEF!"

- Adventure Time

Aww, look at sweet little Sally. So adorable, so innocent...

...wait, where's my wallet?

This is when a little girl takes advantage of the perception that Children Are Innocent to play a bunch of adults for suckers. Sometimes this character will work in partnership with an adult, usually her father, but as often as not she's the real brains of the outfit.

When she grows up, she'll probably become the Decoy Damsel, who uses her beauty to fool people in the same way Little Miss Con Artist uses her cuteness. Compare Deliberately Cute Child and Daddy's Little Villain.

Anime & Manga

 * Blue (Green in the Viz translation) from Pokémon Special started out as this but it has since dimmed down.
 * Panty and Stocking With Garterbelt has one of these as a Ghost, connected to one that looks like a wolf. Sound familiar?

Comics
"Girl: I think I'm worth more than two new dollies per mark."
 * Kiyoko the apprentice thief in Usagi Yojimbo.
 * In one Nodwick comic, the adventurers find a young girl on her own in the woods. Being Genre Savvy, they assume that she's a shapeshifted monster or deity, and she agrees to let them live if they leave their valuables as an offering. Once they've fled, her parents arrive to collect the loot.

Film

 * Little Rock, working with Decoy Damsel Wichita in Zombieland.
 * Paper Moon
 * The title character of the movie Curly Sue.
 * The whole premise of Matchstick Men.
 * It looks like Hitgirl does this in the trailers for the Kick-Ass movie when she dresses up as a Catholic schoolgirl and stands outside the door of the baddies' place.

Literature

 * Addie Pray, from Addie Pray, the novel the movie Paper Moon was based on.
 * One of the many pickpockets Beka catches is a cute little girl with a doll.
 * Minerva Paradizo from the fifth Artemis Fowl book.
 * The titular Markie, from Robert Aspirin's novel Little Myth Marker, is a combination of this and The Mole. She looks like an 8-year-old girl, but
 * A poem titled 20th Street After Dark features a couple of preteen girls who pose as underage prostitutes and then, once the one girl has the guy in a vulnerable position, they mug him.
 * Claudia from the Vampire Chronicles series plays up her eternal childhood to lure in her victims.
 * Lyra of His Dark Materials plays up the innocent eyes on many occasions so adults will believe her. Her act also has shades of Obfuscating Stupidity.

Live Action TV

 * Sarah from Chuck was one of these as a child.
 * One episode of Psych had Shawn and Gus tricked into getting a mall Santa out of prison because a little girl asked them to. She turned out to be "Santa's" daughter and partner in crime.
 * The Suite Life of Zack and Cody had a little girl who helped her father fake an injury and sue the hotel. Turns out she was the brains of the operation, as her father just comes up with the names of their schemes. Meanwhile, she took orders for Girl Scout cookies from the entire staff... none of whom ever got their orders.
 * Megan Parker on Drake and Josh. All the time.
 * The little Japanese girl and her big brother in Hustle who manage to pull a fast one on the protagonists.
 * Katie Knight, Kendall's little sister from Big Time Rush.

Video Games

 * Tewi Inaba from Touhou.
 * Also Mystia Lorelei, who runs a con using her power (singing that causes night blindness) to sell grilled moray eels (purported to cure night blindness, which she removes as they eat).
 * This is probably why the Thief class is open to Moogle units in Final Fantasy Tactics.

Webcomics

 * Used in this strip in Order of the Stick.
 * Amy from Unwinders Tall Comics. She's middle-school-age and a cracker who may or may not be wanted by the FBI.

Western Animation

 * What about Toph in that one episode where the Gaang pulled all those cons on people?
 * Well, she doesn't use Children Are Innocent trick, she uses her earthbending to fix gambling results. Would propably count still, since everyone thinks she is blind and helpless.
 * She uses the "blind and helpless little girl" schtick on Long Feng in Bai Sing Se to get her and Katara into a party to see the king. It doesn't work.
 * Not quite - Katara tried it, Toph just played along.
 * Toph did, however, use it on that customs agent.... before they decided to take the Serpent's Pass anyways.
 * Jessica Lovejoy was this on an episode of The Simpsons. Bart got blamed for all her hijinks because no one would believe that the sweet, innocent preacher's daughter could be so mischievous. Fortunately, she was found out and sentenced to clean the church stoop.
 * Penny from the Adventure Time episode 'City of Thieves' is definitely this, because.