“When I came onto the film on the first day I said ‘OK, what do we do?’ ” Balser recalls. “They didn’t know what to do. I said at least we know we have to use the songs and take a trip on a Yellow Submarine.”

Czechoslovakian artist Heinz Edelman came up with the Blue Meanies and the idea of good battling evil. The writers included Yale classics professor Erich Segal, who would go on to write the blockbuster pop novel Love Story, and an uncredited young unknown named Roger McGough, who would become one of England’s most celebrated poets.

They helped produce a movie full of erudite jokes and classical references — as Pepperland explodes, the Chief Blue Meanie chortles, “I haven’t laughed so much since Pompeii,” and a four-headed dog seems modeled on Cerberus, who guards the entrance to Hades.

They produced an unwieldy amount of material as they experimented, Balser says, including nearly an hour of animation for Lucy in the Sky with Diamonds, a sequence of just a few minutes.

Students swelled the team (“We emptied out the art schools of London to work all night painting animation cels”) as they worked frantically to finish in 11 months — a breakneck pace for an animated film, particularly in a pre-computer era when everything was done by hand.

“It was really by the seat of the pants,” says Balser, whose credits include an animated TV series based on the Jackson 5 and an Emmy-winning film of The Lion, the Witch and the Wardrobe.

“The final script was typed up a week before the premiere. It’s not a way to make a film. And whenever I’ve given lectures and seminars to talk about film planning I make that damn clear. The fact it worked was one in a million.”

But it did work. And the vivid colors, the wildly morphing shapes, the visual expression of mind-bending concepts (the vacuum-mouthed monster that sucks up the world; the dimension-folding Sea of Holes) and the exuberant message of freedom and non-conformity made Yellow Submarine unlike any film before or since.

“This was not animation for children, but surreal expressionistic nonlinear Alice in Wonderland animation,” says Robert Rosenberg, director of the Coral Gables Cinematheque, who was an ardent Beatle fan when he saw the movie at age 12. “That sense of otherness creeping into a mainstream form was pretty delirious.”

Film historian and retired Miami-Dade film librarian Don Chauncey had just finished college when the movie came out. “I don’t know if transcendent is the right word, but it brought everything to a halt,” says Chauncey, who recalls looking at the projection booth and thinking that “the bands of color shining at me were so intense you could almost walk on them.”

Yellow Submarine continues to inspire dreamlike reactions. When O Cinema co-founder and co-director Kareem Tabsch, 32, saw the movie about a decade ago, at New York’s Museum of Modern Art, he was overwhelmed.

“It was unlike anything I’d ever seen,” Tabsch says. “It was like this modern day Fantasia. It felt very contemporary to me – with this odd quality of being old but new.”

He still thinks it’s unique.

“There’s a lot of wonderful animated films now for kids and adults,” Tabsch says. “But I don’t think there’s that artistic braveness we saw in Yellow Submarine.”

That creative daring may be why the movie has transcended the ’60s when so many other pop emblems of the era seem dated.

“It’s such a part of our collective consciousness,” Tabsch says.

Yet the film’s creators weren’t aiming to create an icon – only to unleash their imaginations and make something original.

“We didn’t say we’re going to do this because of this or that – it just happened,” Balser says. “I see how it works with little kids, with teenagers, how it’s engraved in the memory of older people. I think it resonates today, but I don’t know why.”

When Balser saw his handiwork years after finishing it, he noticed many things he could have done better. But he also saw that the mistakes didn’t matter.

“I thought, ‘This is a real fun film.’ That’s the thing I think will keep it going for a long time. It’s a really, really fun film.”