A Review of "Bubble Boy," in Rahway Christina L. Wilson Chris McCarrell as Jimmy, center, with the ensemble. You'll forget many of the songs the moment you leave "Bubble Boy," a musical being given its world premiere by the American Theater Group in Rahway. Still, when you look back on this likable and lightweight show, you'll probably remember the good time you had when you first heard them. In this comedy, based on the 2001 movie of the same name (which was in turn inspired by the 1976 TV drama "The Boy in the Plastic Bubble"), Jimmy Livingston, a young man born with an impaired immune system, lives inside a hermetically sealed room - it is thought that any exposure to germs will kill him. He is tended to by his rabidly overprotective mother and his tight-lipped father, and resigned to a lonely existence until he meets Chloe, a young woman who has moved in next door and starts to visit him. It's no surprise that these two teenagers fall in love, and after Chloe has a change of heart, leaving their California town for Niagara Falls to marry someone else, Jimmy decides to "build a bubble suit/To keep me safe from germs en route" and he embarks on a cross-country trip to win her back. I can't let Chloe marry that brute/I'm out of here. The resulting journey, which makes up the second act of "Bubble Boy," holds the cleverest scenes of this two-hour show. Unlike Act I, set almost entirely inside the Livingstons" home, the outdoor trek throws Jimmy together with an assortment of others, most of them misfits: a crew of daffy cult members, a gang of quirky bandits and an ice cream truck driver with troubles of his own. Using those added characters, the book writers - Cinco Paul and Ken Daurio, who together also wrote the screenplay for the 2001 film, as well as for the "Despicable Me" movies - build funnier situations the farther Jimmy travels. The rare (and welcome) caustic moments, particularly those at a bus station ticket booth, come off as especially droll when contrasted with the warmhearted and chipper outlook that is established in the opening scenes. The music and lyrics, by Mr. Paul, also gain momentum in the second half. After leading up to the inevitable road trip with a few too many light-pop, sound-alike tunes, Mr. Paul's wordplay turns more mischievous, as in the charmingly silly "There's a Bubble Around My Heart," in which the characters expound on their various fears: "There's a bubble around my heart/Not a real one, "cause then I'd be dead/But a metaphorical one instead." Chris McCarrell, as Jimmy, is an easygoing actor with a cheery presence. Early on, when confined to a small space on the stage, he is skilled in using his expressions to generate extra laughs. Gerianne Pérez, as Chloe, is not as adept, though she is an impressive singer, seemingly effortless. Erin Maguire and Benjamin Howes, as Jimmy's parents, employ keen comic timing, while Gabriel Sloyer (who was a standout in "Pinkolandia" at New York's Intar Theater earlier this year) and Alex Grace Paul shine in various ensemble roles. Rachid Sabitri, Marrick Smith, Anita Welch and Alex Chester complete the cast of 10, directed by Jen Wineman at Hamilton Stage for the Performing Arts. The five-piece orchestra, conducted by Brent Crayon, is smooth and supportive of the singers, though at a recent performance Jessica Paz's sound design experienced occasional dropouts and several over-miked segments that one hopes have been remedied. "Bubble Boy" wraps up as anticipated, with a sweet ending that is entirely in line with the rest of its good-natured story. With such a nice conclusion, it seems churlish to speculate how the script might have been even sharper had the writers risked subverting a few of the audience's expectations, or further varied the show's consistently sunny tone. Such chances are hard to take, of course. As it is, this new musical already delivers quite a bit of fun. And that's not easy to do either. "Bubble Boy," by Cinco Paul and Ken Daurio, runs through Nov. 24 at Hamilton Stage for the Performing Arts, 360 Hamilton Street, Rahway; (732) 499-8226; ucpac.org.