Thou shalt not work with children, animals – or an unleashed Ruth Gordon.

Clint Eastwood disobeyed two of those three movie commandments with 1978’s “Every Which Way But Loose,” arguably the most eccentric film in the movie star’s canon.

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The action comedy, Eastwood’s first, should have been the equivalent of Sylvester Stallone’s “Oscar” … or “Rhinestone” or “Stop! Or My Mom Will Shoot.” An unmitigated disaster.

Instead, “Loose” became a surprise hit and one of Eastwood’s most popular films. Credit Gordon, blistering the screen as Eastwood’s scrappy Ma, or Clyde, the scene-stealing orangutan. Either way, Eastwood looked right at home letting his cast snare the laughs.

Eastwood stars as Philo Beddoe, an amateur boxer floating through life in sun-bleached California. He earns extra cash by walloping anyone foolish enough to take him on in a fight, and he practices his skills by polishing off honkytonk bar dwellers.

Philo’s meandering stops when he spots crooner Lynn Halsey-Taylor (former Eastwood squeeze Sondra Locke) at his favorite night spot, The Palomino. The two hook up quickly, but it’s clear Lynn is the kind of gal country singers write about on tear-strained cocktail napkins.

“Every Which Way But Loose” is like one of those country western song sprung to life, with the addition of an oversized ape for comic relief. You can almost see the animal trainer off-screen guiding Clyde (real name: Manis) through his paces, but he’s such a screen natural it doesn’t matter. The film is as cartoonish as Clyde, a collection of broad gags that would make a fine kiddie film if not for all the drinkin’, flirtin’ and fighting.

Philo is a wizard at fisticuffs, and his bare-knuckled bouts perk up the sleepy narrative. So does the appearance of the Black Widow gang, a hapless Heck’s Angels menagerie who keep running into Philo’s fists. The bikers even get their own bluesy theme song, a sad-sack dirge that tells you they won’t lay a glove on our hero.

“Loose” may be all bluster, but it treats the blue-collar California denizens with respect, and the film’s bittersweet coda should have earned the film more respect than it received during its initial run. Director James Fargo also stages the silliness with care, using clever camera vantage points to hammer home the high jinks. “Loose” doesn’t glamorize the West Coast. Instead, we see a side of the Golden State that’s gritty and unvarnished, something another filmmaker might have easily overlooked.

Supporting players like Geoffrey Lewis (father of Juliette) and Beverly D’Angelo (“Vacation”) add to the light touch, but none can match the ferocity of Gordon spitting out a line. The “Harold and Maude” star is simply doing her old dame shtick, but it’s never been put to better use.

“Every Which Way But Loose” inspired a sequel as well as a fresh way to look at Eastwood the Movie Star.