ANGELS on roller skates glide out at the beginning of Arena Stage's new musical "A Wonderful Life," hinting at how the show differs from - but also resembles It's a Wonderful Life," Frank Capra's 1946 American film classic.A musical may sound like a strange mutation of this beloved movie starring Jimmy Stewart that has been seen repeatedly at Christmas on TV since it went into the public domain in 1974. But seeing this Christmasseason musical is like finding a huge, glittery package under the tree and then unwrapping it slowly through two acts with great happiness. The gift contains Sheldon Harnick's book and lyrics with the late Joe Raposo's music. At the center of the musical, as in the movie, is idealistic George Bailey of Bedford Falls, N. Y., who majors in selflessness all his life. He gives up his long dream of a college education in order to save the ailing Bailey's Building and Loan when his father dies and the Depression strikes. On his wedding day there's a run on the bank and he bails the bank's customers out with his honeymoon money. Despite his goodness, it always seems to rain on George Bailey's parade. Finally, he finds himself falsely charged with an $8,000 loss of funds, arrest, and the bank's closing. George, believing himself a total failure, wishes he'd never been born. He prays. When an answer doesn't come immediately, he attempts suicide. An angel named Clarence appears and rolls him out of danger. In the film, the angel is not visible, but his voice or message is loud and clear. In this musical, the angel Clarence is highly visible as a large black man in a dark suit and roller skates. No wings . As the chief angel assures him, he's going to get his wings saving George Bailey. There is a touch of fantasy, lots of bright color, and the addition of some humor in this musical that contrasts with the Depression-era feeling of the black-and-white film. But there are poignant moments too. In one of the most moving - in both the musical and film - Clarence shows George what life would have been like if he'd never been born, how he changed others' lives; how he saved his little brother's life in an accident; how the bank would have folded years ago; how his wife would never have marri ed or his children been born; how many townspeople in Beford Falls would never have had homes or jobs or half a cup of happiness without him. Like Dickens's Scrooge he repents and finds himself on Christmas Eve, not a failure, but wreathed with love from those whose lives he's touched. Bring hankies; in that last scene, people were openly crying. Casey Biggs is spectacular as George Bailey, bringing such humanity, depth, and substance to the role that this might be a drama - until you remember his winning baritone and easy dancing. The multicultural cast includes Brigid Brady as George's loyal wife Mary, Jeffrey Thompson as the irrepressible Clarence, Richard Bauer as villainous Mr. Potter, Ralph Cosham as the saintly Joseph, Halo Wines as George's formidable mother, and Henry Strozier as tipsy Uncle Billy. Sheldon Harnick's book and lyrics are delightful, but the catchy song "Linguine" seems a bit out of sync with the story. Joe Reposo's music, as always, charms the listener in a direct and ebullient way. The merry angel number, "Wings," is the one you come out humming. Douglas Wager, artistic director of Arena Stage, proves once again how inspired he is at directing American musicals like "On the Town." Under his direction this musical has its moments of joy and a holiday lilt. But it also retains the spirituality that's at the core of the story, as George Bailey falls to his knees in a snowstorm praying "Show me the way." Choreography is by Joey McKneely, period costumes by Jess Goldstein, and sets by Thomas Lynch. The original short story "The Greatest Gift," on which the film and musical are based, was written by Philip Van Doren, who couldn't sell it. He turned it into a large Christmas card and sent it to friends. One of them was a Hollywood agent who helped sell it to RKO, where ace screenwriters Marc Connelly, Dalton Trumbo, and Clifford Odets all tried to turn it into a film. But it wasn't a final take until the celebrated director Frank Capra leaped at the story at a time when he was battling a sense of failure himself. Critic James Agee called it "one of the most efficient sentimental pieces since 'A Christmas Carol. Capra considered it his best film, hoped for an Oscar, didn't get one. As Capra, who died last year, wrote in his autobiography, "The Name Above the Title," it was "a film to tell the weary, the disheartened, and the disillusioned; the wino, the junkie, the pro stitute; those behind prison walls and those behind Iron Curtains, that no man is a failure!"