The magic is gone. Like its watermelon-headed hero, “Shrek Forever After” has the midlife blahs. The fourth and final chapter finds Shrek dispirited by the routine of family life with Fiona and their belching, pooping triplets. He yearns for ye goode olde days when he was ferocious and feared.

Viewers will feel nostalgic for the time when he was funny. This no-mojo “Shrek” is to its series what “The Kingdom of the Crystal Skull” was to Indiana Jones.

The original “Shrek” and its two sequels were wise-guy satires of fairy tales, sending up the corny bits while retaining a sense of anything-can-happen amazement. Remember when Princess Fiona trilled a melody so wonderful it made her entourage of bluebirds explode? So do the screenwriters here. They don’t have anything that sly and subversive to offer, but they resurrect the old gag to remind us what the franchise was, once upon a time.

The plot for this weary outing is lifted wholesale from “It’s a Wonderful Life.” Shrek is drawn into a bad bargain by Rumpelstiltskin, whose specialty is magical contracts. Rumple, a prancing, preening pest with the personality of a snarky 12-year-old, cons Shrek into signing away one little day of his life in exchange for a day of independence from mundane family responsibilities. Failing to read the fine print, Shrek forfeits the day of his birth, and discovers that a Shrekless world is a bleak landscape of nasty witches and persecuted ogres, ruled by obnoxious King Rumple.

In this parallel universe, Puss in Boots is a flabby, pampered housecat; Donkey gives Shrek the cold shoulder, and Fiona is a fierce warrior leading an insurrection of her pickle-hued people. Josh Klausner and Darren Lemke’s screenplay lurches between labored and weary as Shrek re-forges the relationships he ran from in real life.

The Shrek movies were sharpest when they scoffed at the Walt Disney tradition, especially the notion that physical beauty signals inner goodness. Here, the series embodies the worst traits of Dreamworks animation: puns, pointless musical numbers, mad-lib plotting and overreliance on celebrity voice casting. Vocal cameos by Larry King and Ryan Seacrest? Seriously?

Computer animation has moved ahead a lot since “Shrek’s” characters were first rendered; the look of this edition is dated. The 3-D inspires a vertigo-inducing broomstick chase, but constructing a clear, concise action sequence is beyond the powers of director Mike Mitchell (“Deuce Bigalow: Male Gigolo.”)

The film has its moments, but they are a child-sized handful: a cute “Wizard of Oz” reference, and the notion that the key difference between living like a pauper or a king is the ability to draw up really confusing contracts. There is exactly one great joke here, delivered by Eddie Murphy’s Donkey in a spat with the Gingerbread Man. The quality of laughter you will hear around that gem is a level above the tepid chuckles the rest of the movie elicits.

The liveliest aspect of the film is the pesky villain Rumpelstiltskin. Walt Dohrn, who also oversaw much of the animation, speaks in a voice that continuously slipstreams from acid sarcasm to honeyed flattery. At least he seems to be having fun. Which is more than can be said for the rest of us in the audience.