The old saw about three being a crowd is the entire joke in “You, Me and Dupree,” a would-be “farce with a heart” about a newlywed couple whose happiness is thwarted by the presence of the groom’s old pal, a slacker who moves into their idyllic new home when down on his luck, and the hostility of the bride’s father toward the groom, who also happens to work for him. The picture boasts a trio of affable leads in Owen Wilson, Matt Dillon and Kate Hudson, but they’re far from enough when the script by Mike LeSieur is so flat and the direction of fraternal team Anthony and Joe Russo so flaccid. This is one trio you should avoid making a quartet by taking a seat in the audience.

Scruffy beach-bum Wilson, of course, plays the third wheel, Randy Dupree, a supposedly lovable lunkhead who loses his job when he takes a week off to be best man at the nuptials of his buddy Carl Peterson (Dillon) in Hawaii. When Carl, just back from his honeymoon with his bride, lovely inner-city teacher Molly Thompson (Hudson), learns of his pal’s plight, he invites him to crash on their couch for a few days, though Molly is understandably skittish. And soon Dupree, though well-intentioned, has messed up the plumbing (cue the potty jokes), caused Carl to tumble off a skateboard trying to relive his childhood, turned the living room into a mini frat house for an evening of football watching, let Molly find Carl’s pornography stash and even managed to burn down the front of the house due to an excess of candles during a romantic interlude. And though by this time Carl has tired of having his chum around, Molly insists that they take him back after chucking him onto the street with nowhere to go.

Her change of heart results from the fact that by this time Dupree has become the shoulder Molly can depend on after Carl is intentionally co-opted at work by her nasty, arrogant daddy (Michael Douglas), who wants to break up the marriage so much that he promotes his son-in-law and then not only saddles him with a design project that will take up all his time but undercuts him at every turn. (He also suggests that Carl take his wife’s name–and have a vasectomy.) There’s something more than a little creepy in Mr. Thompson’s attitude toward his daughter, and the fact that Douglas plays the character in full Gordon Gekko shark-like mode makes it all the worse. Of course, despite the fact that his friend has turned against him–actually suspecting that there’s something between the guy and his wife–Dupree saves the day, and the marriage, in a way that involves a chase through the halls of an office building that’s not just excruciatingly prolonged but badly staged and wretchedly shot in a hand-held style that suggests the person carrying the camera had some sort of physical disability. The cinematography by Charles Minsky is just one of the mediocre technical aspects of the picture, which looks cheesy and washed-out from beginning to end, and features one of those inanely bouncy scores (by Rolfe Kent) that tries to tell you you’re having a good time when you’re merely looking repeatedly at your watch, because the Russo brothers’ lax pacing and the editing by Peter B. Ellis and Debra Neil-Fisher drag things out to nearly two hours–far too long for this sort of thing.

On the acting side, Wilson just repeats, and then repeats again, his familiar likable shmuck shtick, which works better in smaller doses than this, and he can’t entirely overcome the feeling that Dupree’s enormous concern for Carl is, in its own way, as peculiar as Thompson’s for his daughter. Hudson is given very little to do but look sweet and attractive, which she does without much effort. But Dillon is stuck in a hopeless part that forces him to careen abruptly from nice guy to jealous brute and then back again. (There’s something about Carl that just doesn’t compute.) Seth Rogan is intensely annoying as the third member of the Dupree-Peterson circle, though he’s supposed to be the amusingly hen-pecked husband, and Harry Dean Stanton shows up in two tiny scenes as a regular in the bar the boy frequent. Surely there was once more to this character than appears on the screen now, but Stanton plays him so gruffly that you’re not anxious to see what it was.

Go no further if you want to avoid a spoiler about the movie’s final twist. At the end, we learn that Dupree, now out on his own, has become a successful motivational speaker. When we see him giving his nutty spiel before an enthusiastic audience at the close, it’s obvious that he can’t compare with Tom Cruise is “Magnolia.” It’s still a fitting denouement, though, because a viewer would have to be as gullible as the guy’s applauding acolytes to take any pleasure from “You, Me and Dupree.”