8 shows that jump the shark

It’s every TV fan’s worst nightmare — the moment when a favorite series suddenly veers off into bizarro land thanks to a ridiculous plotline and you start asking yourself “what did I ever see in this show in the first place.”

In TV parlance, it’s when the series “jumps the shark.”

The phrase was made famous by the fifth season finale of “Happy Days,” when Fonzie (played by Henry Winkler) inexplicably dons his leather jacket to go waterskiing — where he literally jumps over a shark in his pathwater.

The inexplicable stunt didn’t exactly hurt “Happy Days” — it ran for six more seasons — but it created a phrase for something we all experienced,.

A “jump the shark” moment typically signal that episode when a series has run out of steam and writers are desperate to keep their long-running shows going with something — anything! — that might reinvigorate the action.

In most cases, they go overboard, creating an entirely implausible situation from which the series rarely recovers.

Here are our picks for the latest, most groan-worthy, “jump the shark moments” for shows still on the air.

AMERICAN IDOL

By LINDA STASI

The decision to add a fourth judge to “American Idol” was as good an idea as extra fat on my thighs.

The mere presence of Kara DioGuardi — or more accurately Me-O-Guardi — beginning in Season Eight ruined the wondrously wicked dynamic between Simon Cowell, Paula Abdul and Randy Jackson.

Kara turned out to be as annoying as listening to a squeaky wheel squeal.

This dopey change occurred when the show’s producer Nigel Lythgoe left to concentrate on other shows, and Ken Warwick took over.

In a misplaced effort to change perfection for no reason, Warwick picked someone who might have had the creds — and DioGuardi certainly had the music writing background — but didn’t have the appeal.

In his infinite wisdom, Warwick also made other idiotic changes that season, such as making the finalists don terrifying outfits to perform in horrific song-and-dance numbers that made me feel like I was trapped in a giant Club Med show with no way out.

Paula took a powder at the end of that season and so did I along with millions of other fans.

— Linda Stasi is the TV critic for The Post.

ENTOURAGE

By NICOLE HOMEWOOD

It took six seasons for this worn-in Hollywood bromance to finally go limp.

In season seven, Vince developed a taste for painkillers and coke. Entertaining? Nope. Realistic? Possibly.

But who watches this show for the realism?

Vince’s addiction dulled everything about this show. Ari’s famous barbs have no bite. Drama’s been a cartoon for awhile, now he’s starring in one. E’s staging a career coup. And Turtle’s value as a character is nonexistent.

Even Ari’s long-suffering assistant Lloyd threw in the towel, wanting something better than the same-old schtick.

Quite the self-fulfilling prophecy.

GOSSIP GIRL

By NICOLE HOMEWOOD

Take a group of sexually-amped, uber-rich high schoolers and move them into college and a little change is inevitable. Unfortunately, nothing changed for the better.

Especially when college hardly factors into the equation.

The three-month break in season three proved problematic for “Gossip Girl,” which veered straight into soapy territory. Other shows that start with teenage characters, such as “Dawson’s Creek,” face a similar problem — and it’s hard to solve: how do you grow old gracefully?

This season on “Gossip Girl,” Serena, apparently tired of bouncing between her now-stepbrother (ew!) Dan and Nate, engaged in the first of her fleeting relationships with wholly inappropriate older men, but then returned to Nate after running off with married politico Trip.

Jenny became a drug mule, and Chuck’s presumptively dead mother appeared from out of nowhere.

You can see the evidence that this show jumped the shark— look for the telltale cutouts in Serena’s skintight dresses.

— Nicole Homewood writes for nypost.com

THE BACHELOR

By MIKE BATTAGLINO

This season on “The Bachelor,” we’ll see the main character really jump over a shark tank.

I’d watch that — and root for the shark. Otherwise, “Bachelor,” I’m breaking up with you.

And it’s not me, it’s you — and ABC’s fishy decision to bring back Brad Womack as the catch of the day. Recycling Womack — the Texas bar owner who ended Season 11 in 2007 by jilting both Deanna and Jenni — is a bigger slap in the face to viewers than the one he’s been getting on promos for the Jan. 3 premiere. More than 40 million single men in America and this guy gets another chance? Who’s his agent, Michael Vick?

Anyone who watches “The Bachelor” has to have a preferred pairing for that final rose ceremony. Then they watch the person they think should be picked get dumped in favor of the more attractive one.

But it has to have an ending — even if it’s only to glance at tabloid covers on the newsstand that chronicle the new couple’s journey, from “In Love” to “Wedding Plans” to “He Cheated” to “Breakup!”

If Womack proposes, there’s no way to believe he wasn’t forced to by the show.

And, if we sit through 10 more two-hour episodes and he doesn’t pick anyone again, I’ll jump in the shark tank myself.

— Mike Battaglino is the sports editor of nypost.com

GLEE

By ANDREA PEYSER

Giddy and wickedly subversive, “Glee” waltzed into my living room last season like musical heroin, featuring an addictive cast of hysterically warped singing high-school kids who made me laugh, cry and grateful that the hot ones, such as bad-boy Noah Puckerman (the delicious Mark Salling), were really over 21.

Now, as fast as you can say “receding hairline,” the show is making me retch.

Maybe it was the episode in which Sue Sylvester, played by funny woman Jane Lynch, impersonated the tired and cranky Madonna in an homage to “Vogue.” It got worse when the actual Britney Spears showed up, proving that even scratched and dented celebs can find a support group on network TV.

“Glee” hit rock bottom when it snatched up as a guest star Gwyneth Paltrow, the Oscar-winner most famous for her bowel-elimination tips. An ancient Carol Burnett as a Nazi hunter? Makes me wonder if all it takes to win a guest spot on “Glee” is a faint pulse and bad Botox.

But, I threatened to throw the remote into the fish tank when Santana and Brittany (Naya Rivera and Heather Morris) increased my daughter’s vocabulary, and mine, by engaging in the act of “scissoring.” At 8 p.m.!

“Glee” started with spring-like promise. But at some moment, between the side-splitting scene in which macho dad Burt Hummel (Mike O’Malley) caught gay son Kurt (Chris Colfer) in a leotard singing Beyonce’s “Single Ladies,” and the “please shoot-me — now” episode when Rachel Berry (Lea Michele) transformed into a poor-man’s Barbra Streisand, the show has devolved into the most loathed and feared substance on television: Shark bait.

I’m afraid it’s hopeless.

— Andrea Peyser is a news columnist for The Post.

MONDAY NIGHT FOOTBALL

By PHIL MUSHNICK

Down in front!

Dennis Miller can be very funny. But not on “Monday Night Football.” In 2000, the rage was — and remains — to combine sports with entertainment, a rotten idea. Those who want to watch football in primetime want to watch football; those who want to watch entertainment shows in primetime watch entertainment shows.

Miller began slowly, then weakened. His gags and commentary were forced, as if read from index cards. He made references to people such as Edith Piaf.

Worse, play-by-play man Al Michaels, eager to prove that he “got” Miller, would try to top Miller, try to out-funny him.

Nurse!

The whole thing, which lasted two seasons, was a drag. “Monday Night Football,” already something of a fading ritual as the NFL also played in primetime on other nights, went from must-see TV to take-it-or-leave-it.

— Phil Mushnick is the TV sports columnist for The Post.

GREY’S ANATOMY

By SEAN DALY

In the end, this popular hospital drama will be best remembered for two words: “ghost sex.”

The screws started coming loose for the gang at Seattle Grace in 2008 when Izzy Stevens (Katherine Heigl) began having hallucinatory relations with her deceased ex-fiance, Denny Duquette (Jeffrey Dean Morgan). It got worse when she fell in love with George (T.R. Knight)

(We won’t mention the emergency surgery she performed on a deer.)

The show had its second “what were they thinking moment” in October 2010 when an entire episode was presented as a phony documentary. The ridiculous premise included a double arm transplant!

Now producers are rummaging again in their bag of bad ideas to bring us what could spark prime time’s first ever triple shark jump: a musical episode, scheduled to air next year.

“I’m still nervous about it,” creator Shonda Rhimes has conceded, “because you can do something like this and it can come out not the way you intended.”

I am guessing she may be right.

— Sean Daly is a freelance writer based in LA.

BONES

By MAXINE SHEN

The crime show about a forensic anthropologist and an FBI agent narrowly missed jumping the shark in Season 3 by having a beloved “squint” turn out to be the protégé of a cannibalistic bone collector.

Turned out that plot was a preview for the real jump-the-shark moment, which came the following year.

Throughout Season 4, the cast and crew teased that Booth (David Boreanaz) and Brennan (Emily Deschanel) would finally resolve all their burning sexual tension by actually hopping into the sack, swearing up and down that it wouldn’t happen during a dream sequence or a hallucination. But they didn’t say anything about it not being an anesthesia-induced coma sequence set in a lame alternate universe.

In the season finale, Booth and Bones morphed into married bar owners who get hot and heavy, before helping solving a case involving a dead body at their bar. It gets better: when Booth woke up from the coma at the end of the episode, he had amnesia.

Fans felt duped. “Bones” has yet to recover. If we really wanted AU — done right — we’d be watching “Fringe” instead. — Maxine Shen is a TV reporter for The Post.