There’s a moment early on in "Men in Black 3" when Will Smith’s Agent J sits down next to his longtime partner, Tommy Lee Jones’ Agent K, and bemoans the fact that he’s too old for this sort of thing — for running around New York in matching dark suits, chasing down aliens and zapping them with their shiny metal weapony doo-hickeys.

We’re paraphrasing a bit. But unfortunately, that’s an excellent observation. We’re all too old for this sort of thing — the shtick itself has gotten old, and it has not aged well.

Fifteen years since the zippy original and a decade since the sub-par sequel, we now have a third "Men in Black" movie that no one seems to have been clamoring for except maybe Barry Sonnenfeld, the director of all three. Long-gestating and written by a bunch more people than actually get credited, the latest film shows the glossy style and vague, sporadic glimmers of the kind of energy that made this franchise such an enormous international hit. But more often it feels hacky, choppy and — worst of all — just not that funny. And of course, it’s in 3-D for no discernible artistic or narrative reason.

Smith and Jones don’t seem to be enjoying themselves, either, in returning to their roles as bickering secret government agents. When even the most charismatic actor on the planet can’t fake excitement, you know you’re in trouble. (We’re talking about Smith, in case you were wondering.) The puppy-doggish enthusiasm is gone, and now his Agent J is just weirdly obsessed, after all these years, with determining why it is that K is so surly. K, meanwhile, remains surly and reveals nothing.

But then one of K’s adversaries from long ago, the growling, sharp-toothed alien Boris the Killer (Jemaine Clement of "Flight of the Conchords"), resurfaces and forces everyone to revisit the past. Literally. Boris busts out of the high-tech Lunar Max prison — with the help of his girlfriend, played by Pussycat Doll Nicole Scherzinger clad in dominatrix gear and carrying a cake — to jump back in time and kill the Young Agent K, who put him there.

(Back to Scherzinger for a moment: She’s one of the many nonsensical elements here, one of many characters and ideas that are introduced and then cast aside. She arrives at the prison and approaches Boris’ cell in a beautifully framed opening sequence, then after a great deal of buildup is simply jettisoned. The absurdity of such randomness isn’t even amusing; it just feels sloppy.)

Anyway, Boris returns to the summer of 1969, a few days before the historic Apollo 11 moon mission, and takes out Agent K. Agent J shows up for work in the present day and wonders what happened to his partner; once he figures it out, he jumps back a bit earlier to kill Boris before Boris can kill K. Time-travel plots can make you feel dizzy and nauseous if you try and pick them apart to determine whether they make sense, but once we reach our destination here, the jokes provide no pleasant escape. It’s all super- obvious fish-out-of-water stuff and gags about how ridiculous hippies looked.

"Men In Black 3" begins to address the possibilities of how it must have felt for a strong black man in America during this tense time for race relations, then backs off. There’s also a brief, clever bit in which Bill Hader plays Andy Warhol that might have worked as a separate "Saturday Night Live" sketch. Again, more opportunities squandered.

The best part of our trip to the ’60s — the best part of the movie, period — is the arrival of the Young Agent K. Josh Brolin channels Jones in eerily dead-on fashion, from the bemused Texas twang to reticent demeanor to the slightest facial tics. It’s also an amusing bit of casting given that a) the two actors co-starred in the Coen brothers’ masterpiece "No Country for Old Men" and b) Brolin is supposed to be playing a 29-year-old version of Jones, even though he’s in his mid-40s, and looks it.

As good as Brolin is, though, the novelty wears off quickly, and we’re once again left with the realization that there’s no substance to the script (credited, for the record, to Etan Cohen). And all the familiar and rather flat comic elements lead up to a revelatory climax that comes out of nowhere and in no way earns the sort of heartrending emotion it aims to evoke from its audience.

But the most disappointing part of all: Frank the talking pug is nowhere to be found. The movie is a dog anyway without him.