Brian Truitt

USA TODAY

For its latest animated short, Pixar takes one of its tried-and-true treasure tropes — a box filled with toys and other goodies — and brings it to life.

An unseen creature in a school’s lost-and-found bin helps teach a bully a lesson in Lou, a six-minute short directed by Dave Mullins, produced by Dana Murray and showing in front of Pixar’s next feature film, Cars 3 (in theaters June 16).

With baseballs for eyes and cloaked in a red hoodie, the title monster keeps a watchful eye on the kids on the playground in secret from his box. A boy named J.J. is a real terror, snatching a video game from his classmate and kicking a girl’s stuffed animal into a basketball hoop, and Lou decides it’s time for a high-jinks-filled comeuppance.

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Most Pixar projects come from someplace personal, Mullins says, and his idea came from feeling out of place during his childhood because he moved around a lot.

“You either feel invisible because you don’t know the other kids or you’re embarrassed and you want to be invisible. I thought it’d be really cool to have a character who could hide in plain sight,” says Mullins, an animator on the Cars movies, Finding Nemo and Up who makes his directorial debut with Lou.

His main character’s sole purpose in life is to give things back, and Mullins felt a bully was a perfect foil.

“They’re usually just acting out because they’re awkward or young and don’t have their moral compass set. In a weird way, the bullies sometimes feel invisible, too,” Mullins says. “If you can find out what their motivations are, maybe you can solve some things.

“That’s what I like about Lou: True happiness comes from giving,” the director says. “He gets J.J. to understand that and through that, what J.J. wants really is to be accepted by the other kids.”

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Mullins, 45, ends the short with a “For Dad” dedication: His father died while Mullins and his team were developing Lou's story and influenced the end result.

His dad was a football fan, while Mullins was more of a skater punk growing up, but the common love between the two was going to the movies. So in Lou’s box, there’s both pigskin and a skateboard.

Adds Mullins: “The football ended up becoming a device for J.J. to annoy the kids at the beginning of the film and then connect to the kids later.”