JOHN TUCKER MUST DIE — * 1/2 — Brittany Snow, Jesse Metcalfe; rated PG13 (vulgarity, violence, profanity, brief drugs, brief partial nudity).

When you can't figure out how to end your movie, end it with a cake fight.

That's not meant to give any crucial details away about the film's rather messy conclusion, it's simply a sampling of the supposed insights offered by "John Tucker Must Die."

This idiotic teen comedy settles for being silly and cutesy when just a little bit of snarkiness (a la "Mean Girls") could have saved it. But alas, it's directed by someone, "Dr. Dolittle" helmer Betty Thomas, whose works lack any discernible edge and subtlety.

The title character is a popular teen athlete (Jesse Metcalfe, from TV's "Desperate Housewives") who's been breaking hearts throughout his years in high school.

So three of his embittered exes (Ashanti, Arielle Kebbel and Sophia Bush) begin plotting their revenge, with the intention of using naive new student Kate Spencer (Brittany Snow) as bait.

Using their advice, Kate is supposed to attract John's attention, lure him in and then break his heart. Naturally, things don't go as planned.

Given the sketchy concept and some of the more questionable dialogue, it's no surprise that this script comes from a male, sitcom scribe Jeff Lowell ("Just Shoot Me!"). Needless to say, his take on the female psyche is pretty sexist.

While much of the blame can be laid on him and on Thomas, whose direction can charitably be called workmanlike, the cast doesn't exactly seem inspired.

In fact, Snow (from TV's "American Dreams") is perky to the point of being annoying, while Metcalfe is all smarm and no charm. And who in the world made the lunk-head decision of casting Jenny McCarthy as the mother of a teen?

"John Tucker Must Die" is rated PG13 for crude sexual humor and references (as well as some flatulence humor), comic violence (pratfalls and the like), scattered strong profanity, brief drug content (abuse of hormones), and brief, partial male nudity. Running time: 87 minutes.