If I hadn’t seen it in a cinema packed with children, I’d have never believed “Chicken Run” was a kids’ film.

The conceit, the jaunty Englishness of it all, the very dated references and the homages are all elements only adults could get.

And yet here it is, an Aardman animated marvel that turns 25 this year and becomes what those of us who saw it in 2000 realized in an instant. It’s a classic.

The “Wallace & Gromit” folks looked at Britain’s decades-long obsession with WWII movies, especially POW tales, and sent them up by turning the POWs into chickens and the “escape” into a high-stakes get-away from an egg farm about to transform into a chicken pot pieworks.

It’s ingenious, twee and jolly good fun all around.

Ginger, voiced by Julie Sawalha (the long-suffering daughter on TV’s “AbFab”), is the plucky ringleader, a hen determined to lead a breakout of the concentration camp known as Tweedy’s Egg Farm. She takes her shot with one “plan” after another, conspiring with the Scottish Mac (Lynn Ferguson) to tunnel, climb the fence or trick her way out, leading dizzy Babs (Jane Horrocks), blunt Bunty (Imelda Staunton) and the rest to freedom.

The huffy old RAF veteran rooster Fowler (Benjamin Withrow) cheers them on and insists on “discipline,” “order” and “morale” in the ranks, “What what?”

But every time she fails, Ginger is tossed into the coal bin, “the cooler,” where she bounces a tennis ball off the walls (Steve McQueen style) awaiting her next release. The Tweedys (Miranda Richardson and Tony Haygarth) can’t kill and eat her. She’s too productive as a layer.

But egg farmer Tweedy has his suspicions.

“They’re organizing! I KNOW it!”

Things are dire enough as it is, with any hen who isn’t laying enough destined for a head-lopping. Then the machinery arrives for Mrs. Tweedy to transform a struggling 1950s egg farm into a profitable chicken pot pie factory.

That’s the perfect moment for a rooster, hurtling overhead, to drop into their laps. If he can fly, he can teach them to, or so the reasoning goes. How does Rocky Rhodes (Mel Gibson) manage it? And can he be trusted? He’s a Yank, after all.

“Overpaid, oversexed and over HERE” Fowler huffs, repeating the best British WWII joke describing U.S. troops in the U.K.

Rocky, the “lone Free Ranger,” is hip, cool, a hustler escaped from a circus and all about entertaining the hens as he leads them through pointless flying lessons, calisthenics and the like.

“Flying takes THREE things — hard work, PERSEVERANCE…and hard work!”

They’ll need the help of some POW camp scavengers, packrats Fetcher (Phil Daniels) and Nick (Timothy Spall). Radio, tools, disco lights? Whatever you need, guv’nah.

The glories of the stop-motion animation of Aardman are the sight gags and slapstick tumbles, and attention to hand-animated details — dizzy Poppy (Horrocks) always figures any hen missing (and dead) just went “on holiday.” We always see her knitting with real wool.

Rocky and Ginger have to survive getting caught in the comically complex chicken pot pieworks machinery. Hens in a panic looks exactly the way you’d expect — sans feathers (hard to make out of plasticine).

And then there’s the Britishness of their best films. Here, they rip off “The Great Escape,” give a nod to “Stalag 17” and remember the punchline to “The Colditz Story,” a famous prison escape story that involved wings.

Vintage “Star Trek” Scottish jokes, a morale-boosting dance to “Flip, Flop and Fly” and Mel Gibson riffing on being a roguish flirt and fraud, with a tendency to get punch “drunk” after tumbles both date the film and give it a timeless nostalgia.

It’s more complex than the simple elegance of the “Wallace & Gromit” films, a chattier, more plot centric version of their escape-prone “Shaun the Sheep” comedies.

And for a film buff, the laughs come quickly and often at all the riffs, references and gentle jabs on Britain, Britishness and the singular obsession with “their finest hour,” especially stories about the ingenuity and (pardon) pluck of those trapped in the clutches of sworn enemies who mean to put an end to them.

Long before the requisite 25 years had passed, the ruling was already in on “Chicken Run,” an “instant classic” if ever there was one.

Rating: G

Cast: The voices of Julie Sawalha, Imelda Stanton, Jane Horrocks, Miranda Richardson, Benjamin Withrow, Lynn Ferguson, Timothy Spall, Phil Daniels. Tony Haygarth and Mel Gibson.

Credits: Directed by Peter Lord and Nick Park, scripted by Nick Park, Peter Lord and Karey Kirkpatrick (additional dialogue by Mark Burton and John O’Farrell). An Aardman production, a Dreamworks release on Amazon Prime, other streamers.

Running time: 1:24