In “Shrek Forever After,” the green ogre is frustrated, fat, cranky, middle-aged, depressed and bored. They could have called this movie “Shrek the Film Critic.” But then who would pay $17.50 to see it?

After the frantic spurt of fairy-tale allusions and jokes in the first three Shreks, this one inches along with a few mostly pointless action scenes and the occasional mild pun. That it rips off “It’s a Wonderful Life” isn’t the core problem; it’s merely a symptom of the lazy screenwriting that trickles across every limp page of this fantastically boring script. The 3-D effects look terrific, but I’ve seen Keebler Elf commercials with more story line.

A prologue takes us back to the same moment as the climax of the first “Shrek,” when (it turns out) Rumpelstiltskin is about to trick Fiona’s royal parents (John Cleese and Julie Andrews, both wasted) into signing away their kingdom — but he is foiled because their daughter is elsewhere experiencing true love’s kiss (courtesy of Shrek), which voids the contract.

The psycho Rumpel — or Mr. Stiltskin, as his henchmen call him — schemes to trick Shrek, who is bored by family life (you’ll quickly share the feeling after an endless sequence meant to show how monotonous his existence is) and agrees to trade away one day of his early life in exchange for one day to be free of domesticity again.

Since all Shrek does in Ferris Bueller mode is roar at everyone, this doesn’t seem like much of a trade. (What about a trip to Ogre Vegas to flirt up some showgirls?)

And Shrek is too dumb to realize that if you trade any previous day of your life, it could change the present — which becomes a Potterville-like wasteland because Rumpel took away the day of Shrek’s birth and now the ogre has never existed. At this point, you’ll hear 4-year-olds in the audience muttering, “Seen it all before.”

The aura of freshness on offer in this film is roughly equivalent to what you’d experience walking behind Donkey (Eddie Murphy). Shrek gets to meet the beast again (yawn), then figures out that true love’s kiss will void Rumpel’s contract again (snooze), then meets Fiona again only to discover that she’s the general of an ogre army and has no time for romantic foolishness (zzzz).

Only when we re-encounter Puss in Boots (Antonio Banderas), now a bootless fat housecat who has traded adventure for cushion-y comforts, do things liven up a bit — but the movie repeats (and repeats, and milks) the pleading big-kitty-eyes gag from the second “Shrek.”

Other bits that get gnawed to death: A little kid demands in a funny voice that Shrek “do the roar” (this is used at least five times), Rumpel keeps changing wigs, and the Pied Piper he sends to capture our heroes gets everyone to do silly dances with his flute. Interchangeable witches fly around making mild mischief while Donkey and Puss say things like, “You are a cat-astrophe” and, “You’re ri-donk-ulous.”

The movie’s main strategy for finding laughs is (I kid you not) Lite FM. We get to hear just about all of the Carpenters’ “Top of the World” (!), plus characters keep busting out “You’ve Got a Friend” (twice), Whitney Houston and Madonna.

Tired? This series is as exhausted as Shrek after a day of baby wrangling and diaper changing. Just writing about the movie is making me as dozy as the back row of an eighth-grade math class on a warm afternoon.

Normally there is no reason to take notice when a sequel trying to fire up some publicity bills itself as “the final chapter.” This time, believe it.

kyle.smith@nypost.com

