Just a Kid/Playing With

Basic Trope: A child character is underestimated or dismissed due to his age.
 * Straight: 8 year old Billy becomes a superhero but is constantly laughed at by the villains or scolded by the cops, but that is before he uses his super powers to whoop them all.
 * Exaggerated: 8 year old Billy is told he can't do something simple like play baseball because he is "just a kid."
 * Justified: Children often do not have as much training or experience as many adults, nor are they usually mentally mature or physically built for certain activities, so are naturally doubted by adults who know better when they try.
 * Inverted: Children mock an adult for trying something, like working a cell phone, and call them "too old" for such things.
 * Villains are more worried about Billy than they are about adult superheroes.
 * Subverted: Billy's "powers" are clever tricks from little devices supplied by a sympathetic adult.
 * Double Subverted: The sympathetic "adult" is actually about 10.
 * Parodied: Adults tell children that they are too young for everything like fighting crime, playing sports, tying their shoelaces, or thinking coherent thoughts.
 * Deconstructed: Billy struggles with the transition to adulthood when he enters adolescence, because he doesn't know how an adult is supposed to act.
 * Reconstructed: By the time Billy is an adult, he's already incredibly skilled at what he does because he has had far more experience and practice than other people his own age, and earns the respect he never had as a kid.
 * Zig Zagged: Billy is told he is too young for a construction job but other kids in this world are nuclear physicists or pharmacists.
 * Averted: Children never take on adult roles; adults never question the presence of a child among them.
 * Enforced: "Many of our younger audiences are tired of being told they can't do something. Let's have our protagonist be told the same thing so they can relate to him, and then have them feel a catharsis when he proves them wrong."
 * Lampshaded: "You're just a kid." "Will everybody stop saying that?"
 * Invoked: Billy deliberately overplays his youth to lull his opponents into a false sense of security.
 * Defied: Tired of being told that he was too young to do certain things, Billy gets Magic Plastic Surgery to make him appear much older.
 * Discussed: "We keep telling him that he can't keep time traveling and fighting demons because he's just a kid, but he just won't listen."
 * Conversed: "You'd think that all the adults will stop doubting his abilities after all the cool stuff he did last season."

You can't go back to Just a Kid, you're Just a Kid!