The long-delayed third installment of the aliens-among-us comedy series doesn’t amount to much with Josh Brolin, but it would be a lot less fun without him. Brolin plays the younger version of Tommy Lee Jones’s stern, laconic Agent K, and nails the older man’s unique vocal delivery and granite-faced mannerisms. The effect pales after a while, of course, but the performance is a fun trick to watch.

But otherwise “Men in Black 3” is a fairly limp, lackadaisical affair, directed without much verve (thus continuing Barry Sonnenfeld’s downward career trajectory) and hobbled particularly by the absence of a good villain. In a way the low-key approach is welcome, since it sidesteps the usual pattern of sequels that go for broke in a futile attempt to outdo their predecessors. But the result feels rather undernourished in the mirth department.

Etan Cohen’s script is a time-travel yarn blissfully unconcerned about explanations or coherence. (It makes the “Back to the Future” movies seem like models of lucidity.) It begins with the escape of Boris “The Animal” (Jermaine Clement), one of the aliens Agent K caught years ago (at the Apollo 11 moon-landing launch of 1969, in fact), from his outer-space cell. Boris then uses a device to go back forty-three years and kill Agent K, preventing him from putting a shield around earth that has prevented a planned invasion of the planet since then.

Boris’ plan succeeds, altering earth reality and bringing about the invasion. But K’s long-time partner Agent J (Will Smith) remembers his friendship with the now-absent older man (why is never explained, though we are told the result includes a sudden craving for chocolate milk), and after convincing new head honcho Agent O (Emma Thompson, Rip Torn having literally departed the scene) that he’s not nuts, J travels back to 1969 to foil Boris’ scheme, save K and maintain the protective shield in place.

It’s at this point that the movie abandons the old-shoe camaraderie between Smith and Jones and introduces Brolin as K’s younger self, who of course has to be persuaded that J is who he says he is and join forces with him to stop Boris—definitively, this time. There are a few decent fish-out-of-water bits (a few treading, though very lightly, on the still-evolving, now crudely archaic racial relations of the time), but for the most part what Cohen’s come up with—like a visit to the avant-garde Factory of Andy Warhol (Bill Hader)—is pretty lame stuff. The one really inventive bit involves the introduction of a sweet-tempered alien called Griffin (Michael Stuhlbarg), who can foresee every possible future and only hope that the right one will come about. (He’s also the one who presents earth with the gift of the protective shield.) Griffin is used to introduce into the story yet another of the miracle events of 1969, the World Series victory of the New York Mets, which is nothing more than an amusing tack-on out of left field, as it were. And he also serves as the lead-in to an equally sweet coda that draws a link between K and a very young version of J.

All of this is relatively easy to take, though so ragged in logical terms that it’s almost laughable. Still, the nonsensical plot does make it possible to enjoy once again the genial give-and-take between Smith and Jones, while injecting Brolin’s shrewdly drawn homage to the latter into the equation. (Cohen omits any direct face-off between the younger and aged Ks, which is a bit of a disappointment.) And Smith controls his when sharing scenes with them both. But apart from Stuhlbarg, who’s required to convey little more than a beatific naivete but does that nicely, the rest of the cast is pretty much wasted. In particular nothing is asked of Thompson but the purse-lipped, clipped delivery that’s her natural state. And Clement gives not a hint of amusement to Boris, a surly, hirsute creature whose bellowing quickly grows tiresome. It doesn’t help that the only gag Cohen provides for him is his intense dislike for being addressed by his nickname. Ha-ha.

The picture is decently made from the technical standpoint, with matters made easier for the effects crew by reason of the fact that in a comedy like this, one expects the creatures to look like rubbery constructs as opposed to the real thing. Certainly one has to give credit to whoever was responsible for corralling so many sixties cars in pristine condition. They look brand spanking new lined up along the NYC streets. Cinematography (Bill Pope), production design (Bo Welch), set decoration (Susan Bode) and costumes (Mary Vogt) are all fine, but Danny Elfman’s score is nondescript. One anticipates more inventiveness from him.

If one calculates the mathematical formula that’s been behind release of the “Men in Black” franchise, the years between installments have doubled with each one—the original in 1997, the much inferior sequel five years later in 2002, and this one a full decade after that. If the pattern continues, “Men in Black 4” should appear in 2032. Unfortunately, if this one is anything to go by, that won’t be too long to wait.