By Joan Lowerison | Theater Review

Three unique people — a guy who owns a garage, the schizophrenic sister he’s been looking out for since their parents died in a car crash years ago, and a guy named Sam (as in “play it again”) who clutches a book about Buster Keaton and dresses like he’s in a ’20s Chaplin movie — are the main characters in “Benny & Joon,” playing through Oct. 22 at The Old Globe.

This world premiere musical (with book by Kirsten Guenther, music by Nolan Gasser and lyrics by Mindi Dickstein) is based on the quirky 1993 film starring Johnny Depp.

Benny (Andrew Samonsky) has kept sister Joon (Hannah Elless) on a fairly short leash, because he fears the consequences of her occasional (and unpredictable) lapses from reality if he’s not close by.

We understand why when we see him drop everything at the garage and rush to her side when he hears she’s standing in the middle of the street, directing traffic. While they are very close, he feels trapped, and she feels caged by his habit of treating her like a child.

One night, Joon plays poker with Benny’s friends. When she ends up losing, Benny ends up gaining (or maybe being stuck with) a roommate/boarder named Sam, an eccentric near-illiterate from an abusive background who barely speaks unless it’s lines from favorite movies. But Sam can amuse with some pretty impressive tricks, like “walking” on chairs and hat tricks.

Joon tends to talk in Shakespeare quotes. But Sam, who talks more with gestures than words, seems to “get” Joon better than Benny does in some ways, and soon they start a tentative romance. This makes both Benny and Dr. Cruz (Natalie Toro) — Joon’s psychiatrist, who thinks she should be in a group home — nervous.

Meanwhile, Benny has met failed actress and current waitress Ruthie (January LaVoy). He’d like to get something going with her, but is that possible, with Joon’s unpredictable needs? His buddies at the shop encourage it, but …

These are the human questions at the heart of “Benny & Joon.”

I came away from this musical scratching my head a bit about who these characters really are (they feel a bit one-dimensional), and found in after-show conversations that those who had seen the film didn’t have that problem. So I watched the film.

I now understand why: The film gives us much more backstory, so that we feel invested in, rather than weirded out by, these characters.

Gasser and Dickstein’s music — pleasant though it is — also seems more stuck into rather than being a vital part of the story.

Staging is unusual, to say the least. Set pieces (designed by Dane Laffrey) are rolled on and off (seemingly constantly) mostly by cast members, and sometimes it seems more like a skating show than a play.

But that’s not to slight the uniformly excellent cast.

Hannah Elless (seen in The Old Globe’s “Bright Star”) is convincing as Joon, though I’d have preferred to see more of the “functioning” part of her illness as a painter. It’s clear she has a fine brain, but here she mostly sits, broods or is told what to do. At one point she even goes into a full meltdown.

Andrew Samonsky is good if not totally convincing in a difficult part as Benny, who (we are to believe) is at first solicitous to a fault, but later turns downright mean to the sibling he’s spent his whole life with.

January LaVoy is a joy as take-no-guff waitress Ruthie, and Benny’s friends and workmates, played by Colin Hanlon, Paolo Montalban and Jason SweetTooth Williams, are fine as well.

But the show belongs to Bryce Pinkham’s Sam, who brings magic to everyone, most especially to Joon, who at last feels she’s being treated like an adult.

An offbeat film doesn’t always make a charming, offbeat musical. “Benny & Joon” needs some work to sync the two.

—Jean Lowerison is a long-standing member of the San Diego Theatre Critics Circle and can be reached at [email protected].