The only reasonable explanation for why such a terrific ensemble cast would agree to participate in "The Big Wedding" is that they had a desire to work with each other while making a little pocket money in the process. They certainly couldn't have signed on based upon the cringe-worthy screenplay from writer-director Justin Zackham (who saw brighter days penning 2007's "The Bucket List"), which tops itself every other minute with the sort of odious would-be humor and off-putting behavior to make a person not be able to stand any of the characters in view. And let's get this straight right now: "The Big Wedding" has none of the tough, slice-of-life sting of 2008's "Rachel Getting Married," nor the feel-good vibes of something akin to 1994's "Four Weddings and a Funeral." No, "The Big Wedding" comes closer to reminding of 2007's dumb-as-a-box-of-hair farce "License to Wed." It is either sheer coincidence or a really bad omen that both pictures shamefully waste Robin Williams (2009's "Old Dogs") as an officiating priest.

It is the wedding weekend of young couple Alejandro (Ben Barnes) and Melissa (Amanda Seyfried), and all of their family members are coming together for the big day. Among them: Alejandro's adoptive father, Donald (Robert De Niro), and his live-in girlfriend of ten years, Bebe (Susan Sarandon); Alejandro's adoptive mother, Ellie (Diane Keaton); older siblings Jared (Topher Grace), a virginal OB-GYN, and Lila (Katherine Heigl), harried over her recent break-up and a secret she's been harboring; and Melissa's out-to-lunch parents Muffin (Christine Ebersole) and Barry (David Rasche). With Alejandro's traditional biological mother Madonna (Patricia Rae) dropping in from Colombia, he has a big favor to ask: that Donald and Ellie pose as a happily still-married couple to appease her belief that she gave her baby to a well-adjusted family all those years ago. Naturally, tensions are going to be at an all-time high before the bride and groom even set foot down the aisle.

Adapted from the 2006 French film "Mon frére se marie," "The Big Wedding" flounders on the brink of embarrassment, crossing over time and again as the plotting grows ever more asinine and nothing gels. The film opens with Ellie happening upon her ex-husband about to perform cunnilingus on her former best friend and the woman he left her for a decade earlier, and that's a highlight. From there, the characters, who are supposed to be related or at least have long histories with each other, act as if they've barely met. Each one has their own piddling subplot—Jared, who swore off sex until he met the right person, is about to break his vow with the appearance of his adopted brother's smoking-hot sister, Suria (Ana Ayora); Lila has never gotten over her parents' divorce and has been unable to get pregnant; Donald and Ellie become overly involved in their charade playing husband and wife—or, in the case of the couple at the center of the wedding, none at all. As Alejandro and Melissa, Ben Barnes (2012's "The Words") and Amanda Seyfried (2012's "Les Misérables") are asked to pose as window-dressing.

The rest of the actors have seen better days, too, with Robert De Niro (2012's "Silver Linings Playbook"), Diane Keaton (2012's "Darling Companion"), and Susan Sarandon (2013's "The Company You Keep") all playing half-assed variations on characters they've essayed with much more life and depth in the past. As Lila, Katherine Heigl (2012's "One for the Money") retains the most dignity, perhaps because she's one of the few people on display who feels potentially real rather than a cardboard cutout simulating human form. At the other end of the spectrum, Christine Ebersole (2009's "Confessions of a Shopaholic") is used as a punchline and little else as Melissa's mother, Muffin, who hasn't met a plastic surgeon she didn't like. Forget there being any warmth or legitimate chemistry between siblings, or children and parents, or significant others; even as multiple couples get married by the end, the film makes a convincing case for remaining single.

In "The Big Wedding," there are public professions of love set in front of nameless wedding guest onlookers, punches to the nose, some under-the-table action during the rehearsal dinner, pratfalls in the lake, and a strong-willed woman, Bebe, who is willing to forgive and forget her long-time lover's cheating because he's so gosh-darn lovable and finally has a ring to put on her finger. Were that not enough, lines such as, "Who do you have to lynch for a Cosmo around here?" pass for a version of humor that only a Mississippi slave owner in 1858 would likely find funny. As the faux-upbeat misery comes to a close and everyone tidily reconciles in time to shake a leg at the reception, very nearly nothing that's been witnessed over the previous 85 minutes can be bought for a second. Though a freak gas leak would have been a preferable conclusion to the tale, one must look on the bright side and count his or her actual blessings: at least it's over quickly.