Like its title character, Martian Child is an odd little entity that’s missing something. Adapted from the novel by David Gerrold, this tale of a recent widower (John Cusack) who adopts a young boy who claims to be from Mars is short on the sort of fanciful touches and emotional potency that such a story requires. Cusack is clearly invested in the part, but he never makes a vital connection with Hollywood moppet Bobby Coleman, who seems to have been cast mainly for his adorable lack of key baby teeth.