May 14, 2004 | A cleverly concocted hybrid of conventional romantic comedy and mistaken-identity farce, Breakin' All the Rules is fresh, fleet and funny. Credit writer-director Daniel Taplitz for keeping things light and bright while he spins a scenario of misread signals, rash assumptions, self-defensive feints and self-serving deceits. And while you're tossing out kudos, save a couple for Jamie Foxx and Gabriel Gabrielle Union, the engaging and attractive lead players in this playful entertainment.

The seriously complicated funny business begins when Quincy Watson (Foxx), an L.A. magazine executive, is unceremoniously dumped by Helen (Bianca Lawson), his flighty fiancée. His blue mood turns a few shades darker when his boss, timorous Phillip Gascon (Peter MacNicol), assigns Quincy the messy task of downsizing the magazine's staff. (After reading far too many stories about disgruntled ex-employees, Phillip wants to avoid any risk of violent retribution.) Quincy decides to quit rather than serve as a corporate hatchet man. But he takes his "employee termination" research, adds it to his first-hand knowledge of romantic rejection - and scribbles an angry screed that profitably evolves into a best-selling Breakup Handbook.

The how-to tome is filled with practical pointers for anyone who wants to avoid unpleasant scenes, or homicidal attacks, while severing ties with significant others. Among the most important rules: Announce the breakup at his or her place, so he or she won't leave home to follow you and try to change your mind. On the other hand, if the person is very emotional, or possibly psychotic, end the relationship in a public place - preferably one with lots of security, like a bank or a post office.

Phillip - who publishes the Breakup Handbook under his magazine's imprimatur - seeks private breakup lessons from Quincy to rid himself of Rita (Jennifer Esposito), an alluringly leggy gold-digger who won't take no (or good-bye) for an answer. Evan (Morris Chestnut), Phillip's commitment-averse cousin, also requests help when he mistakenly deduces that Nicky (Union), his current girlfriend, is ready to dump him.

One thing leads to another as the movie gains momentum. Quincy meets Nicky in a fashionable lounge and, without knowing who she is, falls for her. Nicky knows who Quincy is - and, more important, what he has written - but gives him a fake name so she can divine his motives (and, more important, discern his cousin's intentions). Meanwhile, Rita learns about the breakup tutelage that Quincy is providing for Phillip, and vows to win the author over to her side. But when she arrives unannounced at Quincy's house, she mistakes Evan for Quincy. And Evan makes little effort to reveal his true identity after Rita starts to express herself nonverbally.

Inconvenient returns, ill-timed arrivals and overheard telephone messages are just a few of the contrivances Taplitz employs as he keeps his movie moving at a pleasingly brisk clip. The humor isn't always sophisticated - an incontinent dog also figures into Taplitz's bag of tricks - but the dialogue is genuinely witty more often than not, and the actors race through their paces with amusing élan.

In his first official turn as a full-fledged romantic lead, Foxx strikes the perfect balance of frisky mischievousness and comic consternation. Better still, he brings out the best in Union, who once again evidences (as she did in Deliver Us from Eva) impressive range and star presence while coming off smart and sexy, feisty and formidable.

Chestnut makes all the right smooth moves as Evan, while MacNicol and Lawson take a broader-is-funnier approach that stops well short of outright cartoonishness. And even though her role is more caricature than character, Esposito brings surprising emotional resonance to a revealing scene in which Rita matter-of-factly acknowledges her diminishing shelf life as a sexy siren.