BALTIMORE -- Karen and Mary still like to tell the FBI what's hot and what's not. And the girls haven't tired of testing out-of-touch agents on hip-hop songs and cryptic abbreviations teens send across the Internet.
But this spring, the nation's largest law enforcement agency delivered some tough news to the Howard County high school sophomores:
At 16, you're so, like, over.
According to the bureau, Karen and Mary had to retire because they had become too old for their jobs: They had taught FBI undercover agents how to impersonate young teens online to catch prowling pedophiles.
''It's like, not a big deal," Karen said. ''I mean, we're just here to help the kids."
Three years ago, the two teenagers were recruited by the FBI's Baltimore office in a first US approach to fighting crime on the Web. (At the FBI's request, the girls' full names were withheld to shield them from potential harassment on the Internet.)
It all started when one girl's father, an FBI agent, saw his daughter at their home computer. When he looked at her screen, all of the instant-messaging windows quickly disappeared --except for one.
''POS" was the only word on the screen.
The daughter refused to say what the word meant. The father insisted.
''POS," she finally explained, stands for ''parent over shoulder."
Intrigued, the agent then asked one of his undercover agents working on tracking pedophiles on the Internet about the term. She didn't know either.
Then, the girl's father said, he knew it was time to bring in reinforcements.
So his daughter enlisted a friend, and together Karen and Mary designed a hip vocabulary list, crafted a quiz on teen culture, and played hit songs for dozens of agents from around the world.
Undercover agents knew that Internet predators screened potential victims for their knowledge of basic chat lingo such as BTW (''by the way") and LOL (''laughing out loud") and whether pop groups such as the Backstreet Boys were still cool. (Karen: ''That is, like, so five years ago.")
But Stacey Marie Bradley, a supervising special agent for the Innocent Images program in the FBI's office in Calverton, Md., said that without updates from Karen and Mary, her office could have stumbled badly.
''Before they started to help us, we had to kind of wing it," Bradley said. ''They've been amazing."
Cyberstalkers know that they can be trapped by law enforcement. Bradley remembers a suspect, a New York City police officer, who tested her constantly on teen fads in an effort to see whether he was being set up. ''So we need to be current," she said.
Like an actor walking onto a stage, one of Bradley's agents puts on a baseball cap and turns it backward to get into character before he goes online.
The national Innocent Images program started a decade ago after the disappearance of a Prince George's County girl produced two suspects who regularly trolled the Internet.
Since then, agents based here have busted a Navy commander, an elderly man from Alaska, and an Arkansas ''traveler" who had decorated his hotel room with rose petals to lure in his intended victim.
Bradley said the problem is more pervasive than the average parent might think. Innocent Images has opened 14,377 cases since 1995, securing 5,314 convictions through March.
For the last three years, an afternoon with Karen and Mary has become a required -- and popular -- part of the weeklong training for undercover cyber-agents from Texas to Thailand.
Karen and Mary said they weren't broken up over their forced retirement. This summer, Karen will be working as a hostess and Mary's family is moving. College comes quickly enough, they said.
And when they grow up, they expect to come back to the fold. Karen, a fan of ''CSI: Crime Scene Investigation," is thinking about forensic work. Mary might be a lawyer.