Don't call them sidekicks! Young Justice follows the adventures of the teenaged superheroes Aqualad (the team leader, age 15 or 16), Robin (age 13), Kid Flash (age 15), Superboy (age 16 weeks), Miss Martian (age 16 in Martian years), and Artemis (age 15), who have finally gained independence from their leaders and the privilege to start their own covert operations team (of the very popular Justice League). The series is not based on the Young Justice comic series by DC Comics or any comic series in particular, but is simply based on various young heroes of the DC universe - who are sidekicks and protégés of infamed adult DC superheroes (most of which make up the Justice League).
