"My mother's gonna kill me." The 17-year-old girl was worried, and with good reason.

Laetitia Thompson stood up near the end of yesterday's MTV forum on youth and violence and demanded that the president of the United States reveal his underwear preference: "The world is dying to know -- is it boxers or briefs?"

"Usually briefs," William Jefferson Clinton IV told his gleeful audience of 200 college and high school students. The president, shaking his head, sounded just a bit peeved: "I can't believe she did that."

Ah, but this was MTV, the 24-hour music video network that foments teen rebellion and general stupidity while fostering its image as a credible voice of a brilliant, politically engaged young generation. MTV likes to think of itself as the most influential news medium for today's youth -- and it is -- but it's also the proud home of those endearing morons Beavis and Butt-head. Yesterday's "Enough Is Enough" event, taped at a TV studio in Adams-Morgan for airing at 10 last night, echoed a recent episode titled "Citizen Butt-head," in which high school officials do all they can to keep Beavis and Butt-head from addressing a question to President Clinton at a youth-issues forum, but guess who ends up stealing the show? Uh-huh, uh-huh. Shut up, dill hole.

Laetitia, a junior at Churchill High School in Potomac, had intended to ask Clinton a serious question about drug legalization, but underwear -- "that's what people want to know about," she told the press afterward. "He's a real human being. He's very sexually oriented, and people are always interested in that."

Indeed. The media -- notwithstanding its burning interest in what young people had to say on Bosnia, drug laws, guns in school and suicide -- swarmed Laetitia, a willowy blonde whose cover-girl looks probably had nothing to do with her suitability as a sound bite. "How long have you been wondering about Clinton's underwear?" one scribe asked.

The same sort of thing happened during the '92 presidential campaign, when Clinton appeared on MTV and promised to return if elected -- and the quickie random questions at the end made the headlines. ("Clinton: I Would Have Inhaled If I Could Have.") But the White House saw an opportunity for Clinton to reinforce his message on the crime bill now before Congress and to connect with the flannel-clad, nose-ring crowd that helped elect him.

Does the president ever actually watch MTV? "I don't think he watches it on a daily basis, but he's certainly familiar with their programming," said Ginny Terzano, White House deputy press secretary.

MTV President Judy McGrath said Clinton joked with her afterward about the underwear question: "He said, 'I should have said, "I'm too old to answer that question." I can't believe I answered it. But it was funny.' " She added: "That last round of questions is supposed to be the fun, human part of it. We didn't prompt any of the kids, we didn't tell them what to ask."

The audience questions were screened for general content at a rehearsal the night before, however, and the network seemed to seek political balance in selecting the interrogators. "I'm here because they were looking for right-leaning kids," said Spencer Lehv, head of the College Republicans at Columbia University in New York. He's 21 -- older than the age cutoff -- but was allowed in with the admonition from MTV staffers that "I have to ask a question about crime," he said before the show. (He didn't get picked.)

Clinton, standing on a faux-industrial set, addressed the role of pop culture -- including rap music -- in glamorizing violence. He called "Boyz N the Hood" a "great movie ... because it showed you the horrible consequences" of joining gangs. Asked about the impact of gangsta rap, specifically the music of Snoop Doggy Dogg, he said he wasn't sure: "It depends on what the {purpose} of the song is. Is it to make people understand and empathize with and try to do something about these terrible problems? Or is it to legitimize violence and criminal conduct and, ultimately, self-defeating behavior? I just don't know enough to answer it." Clinton said he hasn't heard Snoop's music, but he's read about him in Spin magazine.

Apparently lost on the White House staff was the message of the music used as "bumpers" for the Q&A session. After the president talked about personal and family responsibilities to reduce crime, there were snippets of "Insane in the Brain" by Cypress Hill, a band that glorifies marijuana smoking, and a riff from the Cracker song "Low," which mentions "being stoned."

Early in the program, the president decried cynicism and expressed concern about the suicide of Nirvana front man Kurt Cobain; he prescribed such feel-good nostrums as "Keep your eye on the future" and "There has to be more hope." Later, the sound man cued up Beck's hit "Loser," which exhorts: "I'm a loser baby/ So why don't you kill me."

As the afternoon wound down, and the last reporter grilled Laetitia Thompson about the kind of underwear her father wears ("briefs -- and he looks like Clinton too"), she stood outside the studio waiting for her mom to pick her up. She wore jeans with frayed cuffs, a snug black top and a wide leather belt that belonged in the 1970s. She explained that she doesn't even get cable -- a friend of the family helped her get on the MTV program.

"So what did you do? Tell me what happened," said Lea Thompson -- Mom -- as she approached. "Did you ask your question about legalization of drugs?"

Laetitia demurred. There hadn't been time for a long question, she said. Her mother, dressed in a sharp brown blazer over white slacks, took off her sunglasses and pursed her lips.

Laetitia said: "He's a briefs man, Mom."

"Unbelievable," Mom said. "Tisha, this is unbelievable."

But how could she be angry? Lea Thompson is an investigative reporter for NBC's "Dateline."

"No reporter in Washington would ever dare ask a question like that," she said, almost proud.