Be careful what you wish for ...

Leave it to the Disney Channel to tap into a desire that has crossed the mind of any kid who has had to share a household with an irritating sibling: “Why couldn’t I have been an only child?” In tonight’s charming original movie, “You Wish” (8 p.m.), 15-year-old Alex (A.J. Trauth) gets the opportunity to find out what life would be like without his 10-year-old brother, Stevie (Spencer Breslin), but the results are far different than he could have imagined.

The story is from Jackie French Koller’s book, “If I Only Had a Wish,” which grew out of the author’s experiences with her own two sons. The strong cast of Disney Channel regulars, with a script by Christopher Reed and Cynthia Carle and note-perfect direction by Paul Hoen, combine to make it one of the best efforts of the basic cable outfit’s original-movie franchise.

Trauth (“Even Stevens”) and Breslin (“Santa Clause 2,” Captain Crandall on “Teamo Supremo”) squabble mightily early on as Alex and Stevie, until a magical coin gives big brother a chance to rewrite family history.

At first, the change is the proverbial dream come true. Alex, who has retained his memory of how things used to be, goes from being a high school outsider to king of the campus, with a cheerleader girlfriend thrown into the deal. Stevie, meanwhile, remembers nothing from life with Alex and has been transformed into a child TV star, complete with a new set of Hollywood-style parents (“I have a wonderful mother I just saw last week and a father somewhere in Arizona,” he explains).

But when one of Alex’s pals from the pre-coin days, Abby (Lalanne of “Lizzie McGuire”), rejects him, the dream begins to tarnish.

It’s a breakthrough role for the talented Lalanne, who even sings the movie’s title song. What more could a young actress wish for?