It's an odd coincidence that Martian Child, a fact-based drama about a troubled boy who thinks he's from Mars, should come out around the same time as Lars And The Real Girl, a quirky indie about a grown man who takes a plastic doll for a lover. Both movies are about characters who nurse impossible fantasies, and both feature sane adults who decide the best course of action is to accept those fantasies at face value, trusting the painful emotions behind them will work themselves out over time. In Lars, that strategy comes from a collective insanity that could only happen in a magical place called IndieLand, while in Martian Child, there's some wisdom involved. But both films are too schmaltzy, and worse, fatally obvious about the roots of their fantasists' problems. The healing process becomes as squarely resolved as the end of a Dr. Phil episode.
Still, naked sincerity isn't the worst quality when John Cusack is involved, because he has a talent for projecting earnestness while deflecting the sentiment that threatens to go along with it. He's the film's saving grace as a widowed science-fiction author who tries to work through his grief over his wife—and realize their dashed dreams of parenthood—by adopting a little boy. Though he doesn't set out to raise a "problem child," Cusack's professional vocation naturally draws him to Bobby Coleman, a misfit who believes he's from Mars and spends most of his afternoons hiding in a cardboard box. He wouldn't be a terribly seasoned parent under the best circumstances, and he struggles mightily to nurture a boy with severe abandonment issues. His unconventional solutions show signs of lowering Coleman's defenses, but he faces another hurdle when the adoption board takes issue with his parenting methods.
It's hard to say what, aside from novelty, is gained by having the boy believe he's from Mars, because the core emotion in the film comes from the simple, common premise of an adoptive father and son trying to forge a life together. The science-fiction elements are mere window dressing for a story that's most affecting when it's down to earth, rather than when it's following its heroes' flights of fancy. By the time Anjelica Huston shows up as Cusack's imperious book publisher, the film's resounding anti-conformist message has been spelled out in capital letters. From that point on, Martian Child loses what little mystique it had in the first place.