It's been a good summer for child actors. From "Moonrise Kingdom" to "Beasts of the Southern Wild" and now "The Odd Life of Timothy Green," kids are lighting up the big screen.

It's an especially good thing in this case, because "The Odd Life of Timothy Green" obviously rides on CJ Adams' performance as the eponymous plant child. The movie is the story of, well, the odd life of Timothy Green, a boy born from a collection of traits compiled by a wishful couple (Jennifer Garner and Joel Edgerton) unable to have a child of their own. They write their dream kid's attributes on scraps of notebook paper, put them in a box and bury it in their garden, and a rainstorm magics Timothy into existence.

The circumstances are certainly unusual, but Cindy and Jim Green happily take him in as their own. Sure enough, he has all of the characteristics they dreamed up for their hypothetical offspring, as well as a mysterious collection of leaves growing from his legs. Despite this strange remnant of his earthy origin, Timothy seems to be everything the Greens could have wanted.

Although the couple is more than eager to welcome Timothy into their family, the same can't be said for everyone in their small town. Timothy's earnest naivete gets him into trouble in a number of ways, but what his parents perceive as conflict Timothy takes with all of the good-natured optimism of a Buddhist monk.

His fervent idealism is infectiously engaging, and it helps guide the audience through an otherwise depressing set of events. Both Cindy and Jim's bosses (Dianne Wiest and Ron Livingston) are aggressively nasty, and the same goes for Jim's dad (David Morse) and Cindy's sister (Rosemarie DeWitt). Timothy's arrival sparks direct and indirect conflicts with all of them, but his sunny and precocious nature also helps them see their unpleasant behavior in a new light.

Even though they're responsible for the turmoil affecting the Greens' idyllic little family unit, it's the cast of side characters that really compels the audience's attention. Cindy and Jim are nice, but they're so sweet they're almost caricatures of themselves. They have ups and downs, but their pervasive cheeriness is boring. It's the supporting cast that helps keep "Timothy Green" anchored to a relatable reality. Without them, the movie would have come dangerously close to floating off into a sugar-coated fairytale land on a rainbow expressway.

"The Odd Life of Timothy Green" is an uplifting and whimsical tale, but aside from its feel-good message it lacks the substance to be anything more than a diversion. Even the existence of Timothy himself, who is impossible to hate, is largely purposeless. It's a cute movie, but it's much more suited for family night in front of the TV than a pricey theater.