An index for characters who act, look, think or is in a position different than what is expected for their chronological/biological age. This also includes behavior patterns that don't match their age.
- Acting Your Intellectual Age (rather than chronological age)
- Age-Inappropriate Dress: Dressing in clothing better suited to someone much older/younger.
- Mistaken Age: Someone is mistaken for being older or younger than they actually are.
- Music/Age Dissonance: Someone listens to music aimed at people outside their age demographic.
Acting or looking older than you appear/are
- Adorably Precocious Child: A child who acts like an adult.
- Brainy Baby: A baby who is highly intelligent.
- Child Prodigy: A child who is a genius.
- Cute Bruiser: An adorable-looking asskicker; often a young or a young-looking person.
- Dirty Kid: A child who has more interest in sex than is normal.
- Fille Fatale: A young girl who seduces older men.
- From the Mouths of Babes: Small children say malicious things.
- Kid-anova: A child who manages to get a lot of dates.
- Little Miss Badass: A young Action Girl.
- Little Miss Snarker: A young girl who frequently uses sarcasm.
- Little Professor Dialog: Little kids with worldly experience.
- Never Grew Up: A character literally cannot grow up.
- Really 700 Years Old: A character doesn't look it, but is actually way older than any other living person.
- Teen Genius: A teenager with an unusually high intellect.
- Three-Month-Old Newborn: A newborn baby looks and acts a bit older than that age.
- Wise Beyond Their Years: A child or teen who is more mature and perceptive than one would expect.
- Younger Than They Look: A character looks older than their actual age.
Acting/looking younger than you appear/are
- Absurdly Youthful Mother: A parent is too young (either in looks, chronological age or both) to have had children (sometimes they really were that young).
- Adults Dressed as Children: Adults try to disguise themselves as children.
- Born as an Adult: A being comes into the world as a full-grown adult.
- Dawson Casting: Adult actors playing teenagers.
- Goo Goo Getup: Dressing up like a baby.
- Innocent Prodigy: A child genius who still has the same maturity level as a normal kid their age.
- Immortal Immaturity: An immortal being who acts like a child in spite of their age.
- Kawaiiko: A character who's overly cute and childlike.
- Kiddie Kid: A child character who acts even less mature than the other children.
- Manchild: An adult who acts immature.
- Older Than They Look: A character looks younger than their actual age.
- One of the Kids: A childlike adult who hangs around with children.
- Psychopathic Manchild: A villain or lunatic who acts like a child.
- Rapid Aging: Quickly becoming older and older.
- Really Was Born Yesterday: In spite of their appearance and level of knowledge, this character has only existed for a short time.
Displaying unchildlike/troubling behavior at a young age
- Creepy Child: A child who has something odd or disturbing about them.
- Enfant Terrible: A child who is evil.
- Fetus Terrible: Not even born yet and already they're bad news.
- Laser-Guided Tyke-Bomb: A child is raised to kill someone specific.
- Teens Are Monsters: Teenagers are mean.
- Troubling Unchildlike Behavior: Children who show off behavior that is disturbing because it's not appropriate for children to act that way.
- Tyke Bomb: A child is raised to serve a villain.
Having a position that doesn't match your age
- A Child Shall Lead Them: A child is the leader.
- Child Soldier: Children have to fight in the war.
- Grade-School C.E.O.: A minor who holds a high-ranking position in a company.
- Improbable Age: A character has a profession they're too young to have.
- Promoted to Parent: The oldest child takes it upon themselves to parent their younger siblings.
- Young Entrepreneur: Child who is good at getting other people's money.