Hollywood has gone square! It all started last winter, when Focus Features ran newspaper ads for Eternal Sunshine of the Spotless Mind with a checkerboard of movie stills and critical praise. ''The boxes provided a system to highlight all these reviews,'' explains Focus' David Brooks. ''And we played with yellows and blues [for] sunshine and sky.'' Months later, Fox Searchlight came out with a quote-filled pastel-checkerboard ad for Garden State, followed by an I [HEART] Huckabees poster showcasing its ensemble cast. Now Miramax has squared off: Ads for J. Lo's Shall We Dance? mix hyperbolic kudos (''Utterly entertaining!'' --Wireless magazine) with shots of Richard Gere, Susan Sarandon, and Mya. ''There are only so many ways to incorporate a bunch of images,'' says Miramax's Amanda Lundberg. ''You try to be original, but if it looks similar to another ad, what can I say?'' Besides, since when has Hollywood been about originality?