It’s becoming increasingly difficult to recall that once upon a time Eddie Murphy was actually funny. Now, except for the occasional uncharacteristic turn like his Oscar-nominated performance in “Dreamgirls,” his work has become virtually insufferable—he’s like a higher-rent version of Carrot-Top or Pauly Shore. The only question he leaves you with is which is worse, “The Adventures of Pluto Nash” or “Norbit”?

Or “Meet Dave”? This gimmicky one-joke comedy takes a well-deserved place in the pantheon of Murphy mega-bombs. No accident, perhaps, that it’s directed by the same guy who helmed “Norbit.” (The fact that Murphy chose to work with him again is ample evidence of a serious lack of judgment.) “Dave” isn’t obnoxious and offensive in the way that “Norbit” was, but it’s equally dumb.

The premise itself is terrible. Murphy plays the Lilliputian commander of a spaceship sent to earth to retrieve an orb that will, when released into the ocean, sap them of their salt, which the mini-invaders need to power their home planet of Nil. The ship is in the form of a huge robot—also in the form of Murphy—that will interact with the locals to find and unleash the orb. In one of those idiotic coincidences beloved of lousy screenwriters, Robo-Murphy, or Dave as it comes to be called, just happens to get run down, and then adopted, by Gina (Elizabeth Banks), mother of Josh (Austin Lynd Myers), the kid who found the device (this in New York, where the odds of that happening are about twenty million to one). Josh and Dave bond as they try to track down the schoolyard bully who stole the orb and Gina becomes interested in the “guy,” too, despite his oddities and quirks. But Dave has sparked the interest of a cop (Scott Caan) who believes in extra-terrestrials and is anxious to track him down.

Meanwhile in the ship the captain, who controls the robot’s voice and movements via his crew, finds himself becoming enamoured of earth ways and wary of the effect his mission will have on the planet. And most of his crew are affected, too. His cultural officer (Gabrielle Union), who’s obviously in love with her boss, gets more obvious about her feelings. Others get interested in Broadway show tunes (cue the gay poses), or hip-hop (ditto ghetto slang), or…whatever. That spurs action by the goofy No. 2 (Ed Helms, of “The Office”), who leads a mutiny to take over the ship and complete the mission.

Most of the supposed humor here arises from the white-suited Dave’s inept attempts to conform to earth customs that are utterly foreign to him. It’s a gag that runs dry fast, but both it and his warming relationship with Gina and Josh might have worked better if the whole picture weren’t directed in such a slipshod fashion. The timing is almost always off—a sequence set in Old Navy (one of too many product placements) is excruciatingly slapdash and drawn-out, and isn’t funny to begin with. There’s also a hefty seasoning of the puerile potty humor designed to appeal to kids nowadays, though since a robot’s involved, of course, it’s all purely mechanical.

The earth-based stuff, however, is positively brilliant compared to the awful scenes on the ship, where everybody is stiff and inhibited until the earth’s freewheeling influences kick in. The material is several leagues beneath sophomoric, filled with the crudest stereotyping and staged in a stilted, overemphatic style that makes the dreary stuff all the more painful.

Brian Robbins’ lackadaisical hand is also to blame for Murphy’s dreadful performance, which is all grins, grimaces and bad slapstick, shot for the most part at too close a range by cinematographer J. Clark Mathis. Union is her usual blandly pretty self, Banks is wasted, Myers isn’t the adorable tyke the producers apparently believe, and Caan comes on too strong. The worst indignity, however, is suffered by Helms, who takes his already-hyper “Office” shtick up several decibels, and Pat Kilbane, as the security officer who goes all swishy.

“Meet Dave” looks chintzy, too, with the inner-ship sets especially bad, as though they’d been purchased from a shuttered modernistic hotel. But it’s all of a piece with what’s played out on them. This is a flat, lame excuse for a family comedy, just one more nail in Murphy’s movie career, and an introduction you should definitely avoid.