GLOUCESTER – After 42 years what can be said about “You’re a Good Man, Charlie Brown,” playing this month at the Gloucester Stage Company?It’s a good play, Gloucester Stage.In fact, it’s not just good, it’s the quintessential 20th Century musical revue. It’s actor-proof, musician-proof and director-proof and if by some chance the world comes to an end after a performance of “You’re a Good Man, Charlie Brown,” the people at the show just might be okay with it.Charles Schulz based the “Peanuts” comic strip on the concept that children and pets – beagles, anyway – think about their world in far deeper terms than grownups realize. The lives of the people in the strip are sad but ultimately reassuring. In this revue Charlie Brown is praised as a good man. He sets out to see what that really means and after a day of comical setbacks, including a kite-eating tree that really crunches, his friends praise him again – and for the moment he accepts that.The GSC version features Mary Callanan as an ultra-loud Lucy Van Pelt, Steven Gagliastro as the ultimate well-intentioned Charlie Brown, David Sharrocks as Snoopy, the beagle with the heart of an adventurer and Arlo Hill as Schroeder, David Krinitt as Linus and Katie Mulholland as Sally Brown. All are making strong GSC debuts, trusting the material and their imaginations and their inner children.Two have stories worth mentioning. Krinitt, who goes through the play carrying a security blanket, has a photo of himself dropping a pacifier he was much too old for into a trash can. Gagliastro, a former elementary schoolteacher, recalls a bright kid in his class dealing with rejection optimistically.The play kicks off GSC’s 30th season with a happiness that belies the economic news – and the theater is subsidizing tickets for city children so that they can attend.