There's a TV ad for X2: X-Men United, the film that made a whopping $155 million worldwide in its opening weekend, in which a pretty little towhead freaks when a boy of 8 thrusts out his tongue.

Because this brat is one of the film's misfit mutants, his licker is forked, lizardlike. Not only does this reptile tongue freak the towhead, it also unnerves my 6-year-old, who's not afraid of much except tarantulas.

You might well ask why I'd expose her to an ad for a PG-13 movie. I'd ask the same of Twentieth Century Fox, the studio behind X2, which is regularly running the spot during Nickelodeon's Rugrats, the animated series aimed at kids 2 through 11. Unfortunately, it's not returning calls.

Just a slip of the tongue? More like a loophole in the fine print.

In 2000, after the Federal Trade Commission found that Hollywood routinely marketed films rated R (restricted to those 17 and over unless accompanied by a parent) to underage children, the Motion Picture Association of America pledged it would no longer target kids in advertising violent restricted fare.

Alas, this pledge did not address violent films rated PG-13 (parents strongly cautioned, some material may be inappropriate for those under 13), though the FTC complained that target-marketing of PG-13 films to children under 12 was common.

Since X2 - which is really good but intensely violent, not to mention candid about the hormonal urges that come with adolescence - is PG-13, ads for it on children's shows do not violate the letter of the MPAA promise.

But certainly they violate the spirit of that pact.

"It's not a spiritual document," said MPAA spokesman Rich Taylor. The 12-point pledge "is a specific response to a specific type of film."

While most parents would applaud the film studios for their swift response to the FTC where ads for R-rated material are concerned, most would also agree with Sen. John McCain (R., Ariz.) that the MPAA's guidelines are "full of loopholes."

Clearly, the entertainment industry's "self-regulation practices are not consistent with their marketing practices," as Stanford business professor Sonya A. Grier put it in a 2001 paper in the Journal of Public Policy & Marketing.

Most reasonable people would agree that X2, an angst-ridden film with a boy fire-starter, a teen who sucks the life out of any boy who kisses her, and a Beastman with retractable razor-sharp steel claws that make coleslaw of his foes, is not suitable for a 6-year-old, the median age of Rugrats fans.

So here we are. An R-rated movie can't be marketed to most teens. But a PG-13 film can be marketed to 'tweens and 2-year-olds, presumably a more vulnerable audience.

Speaking as a movie-lover and a parent, I think Fox is exploiting a loophole in the MPAA pledge. Whether it's crossing an ethical line between broadly marketing a product and exploiting impressionable underage consumers I leave to the conscience of its executives.

Like the little X-boy in the ad, Hollywood speaks with forked tongue.