How Do You Talk to Teens? On Their Terms.

The agency has certainly learned how to appeal to its teen panelists. "North Castle is awesome," says Geoff Hawes, 17, who attends Wilton High School in Wilton, Connecticut. "When they'd come to our class, it was a break in the day. They played cool games with us, and they brought us presents." But the agency also knows how to listen.

It was in its teen panels that North Castle first heard the buzz about South Park. North Castle made media buys during the show early on, when the program was charging only $20,000 a spot -- a sixth of what South Park was charging by the end of the first season.