Dirty Kid

Near opposite of the Dirty Old Man, where a kid is ridiculously young, but still has some signs of... "interest".

What's most notable is that often, kids or babies are allowed to cop a feel, simply because it's said that they don't understand what they're doing.

See also Kidanova, which deals more with the romantic aspects, as opposed to the sexual ones, and Fille Fatale, his more sexualized Distaff Counterpart.

Not to be confused with The Pig Pen, who is filthy in a different way.

Examples of Dirty Kid include:

Anime and Manga

Johji from the Death-T arc in Yu-Gi-Oh!.
Shin from Crayon Shin-chan.
Momoka from Mawaru Penguindrum. She went missing as an elementary schooler. Her Diary is very detailed and specific about how her future life would have gone. This includes sexual activities with her prospect Victorious Childhood Friend, Tabuki.
Dai Daichi from The Family's Defense Alliance. Whether being the continuous skirt lifts he gives to his teacher in every episode or the fact that he has a naughty picture collection in his room, Dai definitely plays this trope straight. The opening of the show even has him groping all the female characters of the show (two being part of his family) often resulting with violent repercussions.
One Piece has Momonosuke from the Punk Hazard Arc.While taking a bath with Robin and hugging onto Nami's breasts , he comes off as an innocent child.... that is until he gives off a smug smile shows he has a dirty mind. This does not sit well with Sanji, Brook or Kin'emon
Pastel plays this off within the first chapter, when the kid named Okuto falls purposefully onto the main female lead,Yuu .He ends up grabbing her breast , infuriating the main character Mugi.
Shirai Kuroko from A Certain Magical Index and A Certain Scientific Railgun, a first-year junior-high student who in the earliest stories was pretty much defined by being sexually interested in her roommate. (She became a more rounded character later, but she's still hot for "big sis".)

Baby Herman from Who Framed Roger Rabbit?. He complains, at one point, about having "a fifty-year-old lust, and a three-year-old dinky."
- But Baby Herman is really that old, he just looks like a baby.
- The character he plays as in the shorts may have elements of this, though, with Roger finding an adult magazine (complete with centerfold of Jessica) in his carriage at some point.
In telling his origin story, Don Juan Demarco claimed to have started out this way (but he was lying).

Robert Heinlein's Stranger in a Strange Land. When he first arrives on Earth, Valentine Michael Smith is a child in an adult's body, knowing nothing of human culture. While he's being bathed by a nurse he innocently touches her breast.

Lily of How I Met Your Mother is a kindergarten teacher; in the pilot episode, she comes home with a painty handprint on her (white) shirt. Three guesses where.

The South Park kids, though they suffer from Ping-Pong Naivete, except Kenny, he is always this trope (when the matter is relevant at least).
Bart Simpson (ditto).^[context?]
Stewie Griffin from Family Guy (ditto).^[context?]