What makes a French sex farce fall flat? Translating it into English and turning what was an amusing trifle into a crass, crude, mean-spirited, smarmy mess. How bad is it?

So awful that even the star-studded, multi-generational cast can barely stay afloat.

"Marriage is like a phone call late at night," intones Robert De Niro, as the dysfunctional family story begins.

"First comes the ring, and then you wake up." Missy (Amanda Seyfried) and Alejandro (Ben Barnes) are getting married. What complicates their nuptials is that Alejandro was adopted as a young boy from Colombia and raised by the Griffins, an upscale East Coast couple who already had two older kids Alejandro's devoutly Catholic, biological mother (Patricia Rae) is coming to the wedding -- but he never told her that his adoptive parents, Don (De Niro) and Ellie (Diane Keaton), got divorced and Don's been happily cohabiting for the past 10 years with Bebe (Susan Sarandon), who was once Ellie's best friend. Because they all love Alejandro, they agree to "pretend" the divorce never happened. Predictably, the charade backfires when lewd, lecherous Don and giggly Ellie once again share the master bedroom.

Meanwhile, there are the other now-grown Griffin children: unexpectedly pregnant Lyla (Katherine Heigl), who's just separated from her husband, and Jared (Topher Grace), her 29-year-old still-virginal brother, a doctor who immediately falls for Alejandro's sexy, skinny-dipping Colombian sister, Nuria (Ana Ayora).

More Information

Fact box

Adding to the turmoil are the parish priest (Robin Williams) and the bride's prejudiced parents (Christine Ebersole, David Rasche) -- but whatever farcical elements existed have been muted.

Based on Jean-Stephane Bron's "Mon Frere Se Marie" (2006), it's implausibly, yet formulaically scripted and ploddingly directed by Justin Zackham, born Justin Eglowsky in Connecticut. (He switched to his mother's maiden name after his parents divorced.) His credits include writing "The Bucket List," "One Chance" about "Britain's Got Talent" winner Paul Potts, and the FX series "Lights Out."

On the Granger Movie Gauge of 1 to 10, "The Big Wedding" is a turgid 2. Quickly decline this bizarre invitation.