In the natural world, parents raise children, keeping them healthy and happy. Not in “Raising Flagg.”

In this world, children must revive their parents from unhappiness and teach them the life lessons they were never taught.

Alan Arkin (Catch-22, Edward Scissorhands, Gattica) plays Flagg Purdy, a man with all the hallmarks of age: baldness, salt and pepper grizzle, deeply etched cheeks, dark bags under his eyes. This is a guy who’s lived awhile. But for all his years, Flagg is pretty immature.

He’s short tempered: hollering like a schoolyard poor-sport when he doesn’t win checkers. He’s needy: demanding lots of attention from his patient wife, Ada. He’s delusional: sulking in bed with an imagined illness, just like a child would.

Arkin does a tremendous job playing Flagg, shuffling from scene to scene, barking insults from bed, weeping when people discard his precious principles. Even though, he’s the anti-hero, you like him right away, which is a credit to the writers, Neal and Nancy Miller.

Unfortunately, not all the characters were developed as fully as Flagg. In particular, the Purdy children come off underdeveloped. This undermines the film’s marketing phrase: “The Kids Are Grown Up, Now It’s Flagg’s Turn,” not to mention the central theme of the film. We’re supposed to believe these are complete mature individuals, but they’re mostly just flimsy cutouts of characters compared to Flagg.

We meet Jenny and Grace first. Jenny is in high school and embarrassed by her father. In many aspects she’s almost at Flagg’s level of maturity. She’s ill-tempered and craves attention. Grace is a bit more subdued, a mediator between Jenny and Flagg.

Next there’s Rachel played by Lauren Holly (Dumb and Dumber). She’s mentioned prominently in the opening credits, but her role is unexpectedly anemic. At most, she has ten shrill lines in the entire movie, all of which either make reference to her job as a real estate agent or her beef with older sister Ann-Marie. You never get to know anything more about her, which is a real disappointment.

The same goes for Edgar Purdy, played by Alan Arkin’s real life son Tony. Edgar is a preacher, influenced heavily by religion. That’s all you get to know about him.

Travis and Ann-Marie are also pigeonholed into their one-dimensional characters, Travis a hippy environmentalist, and Ann-Marie, a radio psychologist. These characters don’t ever get beyond repetitious clichés. For such a diverse crowd it seems some entertaining clashes would ensue. As it turns out, the characters simply act bland around one other.

What you’re left with is mixed bag, a film not unlike it’s central character, developed in some aspects, but immature in others.