Eighteen years to the day after the final episode of MacGyver aired on ABC comes comedian Will Forte’s belated parody MacGruber, expanded to 89 agonizing minutes from a recurring Saturday Night Live sketch. Despite a handful of early reviews that proclaimed it “the best SNL movie since Wayne’s World” – hardly high praise, but misleading all the same – MacGruber was withheld from most critics until hours before its release. Now we know why.

The common complaint about SNL-inspired movies is that five-minute sketches rarely hold up as feature-length productions – the jokes, often based on a single fragile conceit, wear thinner than thin. In keeping with that dubious tradition, MacGruber pokes fun at Richard Dean Anderson’s impossibly resourceful secret agent, who seemed capable of crafting homemade explosives out of twigs, berries and a deck of playing cards.

The joke here – that MacGruber, Forte’s mullet-sporting lookalike, is an ineffectual buffoon, all bluster and no bite – is stretched well past the breaking point in a movie that lazily squanders its most obvious setups. We know, for instance, that MacGruber will assemble his own bomb – in this case, out of a tennis ball. When he does, it fizzles.

Where’s the twist? MacGruber is clearly incompetent, so we expect his dim-witted schemes to fall flat. That they do, in stunningly predictable fashion, speaks to the movie’s lack of imagination. So too does its ponytailed villain, Dieter Von Cunth (Val Kilmer), whose name is pronounced with a silent H. (“Pound that Cunth” is our clownish hero’s rallying cry, repeated often in case we missed it the first time.)

MacGruber tosses out so many zingers and juvenile sight gags (including Forte, in the buff, with a celery stick lodged in his derriere) that a few were bound to find their target, and so they do. The best of them suggest the peculiar talent for absurdity of screenwriter Jorma Taccone, who co-wrote the movie with fellow SNL alums Forte and John Solomon.

As he proved in the far funnier Hot Rod (2007), Taccone, a founding member of the Lonely Island comedy troupe, is capable of finding humor beyond the confines of a limited premise, often in throwaway scenes redeemed by the sheer audacity of their silliness.

MacGruber has some of these, but not nearly enough to fill the vast empty spaces. Instead, we are force-fed a too-generous helping of Forte, stooping to regrettably shallow depths for laughs that rarely come, and dragging co-stars Kilmer, Kristen Wiig and an embarrassed-looking Ryan Phillippe down with him.