Addison — There are three musicals at this year's Out of the Loop Fringe Festival. One is an adaptation of a comic book and uses '80s pop hits. Another involves a show-within-a-show about a killer shark. And there's one about a 9-year-old with leukemia.

Guess which one is the most fun?

Yep, it's the cancer one, Dani Girl. Especially if your definition of "fun" includes terrific songs, lovable characters, a concept that manages to be heartwarming but not maudlin, and an ending that will have you smiling through tears. It's truly one of those "you'll laugh, you'll cry" situations.

The musical, with music by Michael Kooman and book and lyrics by Christopher Dimond, comes to Loop from Greyman Theatre Company, created in 2010 by Baylor University students. That would make it one of three groups at this year's Loop that sprung from BU, along with Second Thought Theatre and Rite of Passage Theatre Company.

Dani (Rachel Brown) is the girl with cancer, and the story takes place in the hospital room she shares with another young cancer patient, Marty (Joshua Gonzales). Both know their diagnosis is grim, but they have their vivid imaginations to help them overcome that. Dani has a crafty guardian angel, Raph (Matt Tolbert, who plays other roles). She eventually introduces Marty to him, and they're singing songs about imaginary worlds, hair loss and death while on a quest to figure out "why cancer is."

Dani's Mother (Emily Christine Smith) checks in, and has one of the show's more heartbreaking songs, near the end.

The audience knows that these kids will succumb to the illness, and the show's creators count on that. Dani Girl does what musicals can do better than almost any other art form: Provide joy and laughter in the face of an unhappy ending.

It helps that this cast, under the direction of Kelsey Ervi, gets it all right. Brown captures the notion of this girl who's determined to dream her way out of the unfair hand life has dealt her. Gonzales is equally brave and youthful, and Tolbert gives us several characters that we grow to love, if not instantly. And they all, along with Smith, sing the songs beautifully.

Many of the tunes are melodic and hummable, something missing in too many new musicals. A few of them, such as "Requiem for a Bear" (about Dani's stuffed bear, Mr. Fritz), and a number toward the end in which Dani and Marty ponder getting it all over with by overdosing on Flintstones vitamins ("Side by Sui-cide") are haunting.

If that sounds depressing, trust, it's not. Dani Girl is good for the soul.

◊ Click the calendar link above to see future performances for Dani Girl, which plays in the Addison Theatre Centre's Main Stage. View a full Out of the Loop Fringe Festival schedule here.

Here's a trailer for the Greyman production at Loop: