Real-life teenagers do not look like the cast of Gossip Girl. There's a simple reason for that: The elite New York high schoolers who constantly fought with one another while being chauffeured around Manhattan in the classic CW show were played by adults. Blake Lively, who played high school It Girl Serena van der Woodsen, was 20 years old when the pilot aired, while Leighton Meester, who played the evil-but-brilliant Blair Waldorf, and Penn Badgley, who portrayed lonely boy Dan Humphrey, were both 21 years old.
In terms of deceiving audiences into believing that grown adults are in the throes of their teenage years, Gossip Girl was not the worst offender. Glee expected us to believe that a 27-year-old Cory Monteith, 23-year-old Dianna Agron, and 23-year-old Lea Michele were all still in high school, while Pretty Little Liars cast 24-year-old Troian Bellisario and 23-year-old Shay Mitchell as suburban teens being stalked by a nameless enemy.
This long-standing Hollywood ruse of casting definitely-not-pubescent adults as teenagers is seemingly ubiquitous; if an alien were to learn about the human aging process by simply watching mainstream film and television, she would be bewildered to arrive upon Earth's surface and realize that adolescents are not all gorgeous adults, and that many have braces, acne, or both. The fact that adults play teenagers has become such a commonly recognized trope that the internet has named the phenomenon "Dawson Casting," in reference to the much-older-than high-school-aged cast of Dawson's Creek.
There's a simple reason for this, according to Todd Thaler, a casting director on films such as Billy Madison, Because of Winn Dixie, and Maid in Manhattan. "It's all because of the labor laws. The number of hours that children are allowed to work are highly restricted, which limits the amount of time that producers can actually have adolescents on set," he explains. Compounding that difficulty is that "within those limited hours that children can work, part of that time includes education, rest, and meals."
Uncertainty about how a child actor will age and questions of children's temperament and work ethic also motivate casting decisions, he adds, but the most important and deciding factor is labor law. "In the end, many casting directors choose to go with an 18-year-old because they they can be on set and working for say 16, 18 hours," says Thaler. (It's different, of course, when the cast is meant to be visibly young. When Thaler was working on Because of Winn Dixie, a story about a 10-year-old and her dog, getting an adult to play at 10 year old was out of the question; this is also why all of the kids on Stranger Things are actual kids.)
To honor the legacy of bizarrely old teenagers in television and film, Broadly investigated the ages of the actors on several classic and beloved shows and movies about teenagers, including Gossip Girl, Glee, Dawson's Creek, Pretty Little Liars, Buffy the Vampire Slayer, The OC, Gilmore Girls, Riverdale, Mean Girls, Clueless, and The Breakfast Club.
The show with the most glaring disparity was Buffy the Vampire Slayer, with an average age gap of 8.25 years. Gossip Girl had the smallest average difference: 3.7 years. In some shows, like Gossip Girl and Pretty Little Liars, there is one cast member who's under 18.
Actual teens are highlighted in the graphs below: