Eric William Morris, Nicole Parker, Beth Leavel, Heidi Blickenstaff, and Jon Patrick in Dog and Pony.

Rick Elice and Michael Patrick Walker are the multi-talented, mega-award-winning creators of Jersey Boys, Peter and the Starcatcher, and Altar Boyz. Their world premiere musical isn’t a dog. But, even with a top flight cast, expert design work, and Roger Rees directing, it needs to pony up.

If the musical were a horse race, it stumbles out of the gate, gets boxed in along the rail, and runs the last six furlongs at bullet speed.

Translation: Dog and Pony takes seemingly forever to start. It flits from here to there, goes on and on about collaboration and writing amid loads of backstory. Then, thanks to two spectacular minor characters, it finds its legs and sprints home with three show-stoppers.

Nicole Parker as Mags, Jon Patrick Walker as Andy, Eric William Morris as Jeff, Heidi Blickenstaff as Jane, and Beth Leavel as Rhoda in Dog and Pony.

Mags and Andy co-wrote 11 hit movies. They had a creative synergy, so why did they split up 10 months ago? Burn out? Were they secret lovers all along — are those white bathrobes from the Algonquin Hotel a dead giveaway? Or was working on the movie, American Madhouse, the wedge that caused the great divide?

The musical touches on an interesting subject: can an adult man and woman be close friends, or colleagues, without a sexual component? For those with traditional gender-lock, the answer’s no. To the spouses of such people the intimacy must generate suspicion, at the very least, and, at the most, tabloid horror.

After much talk — they even define themselves for you several times (she’s a “work spouse” workaholic; he’s vanity personified) — Dog and Pony begins when Beth Leavel steps on stage. She plays Andy’s controlling mother Rhoda (a la Valerie Harper’s Rhoda Morgenstern?) and has more funny lines than a Neil Simon comedy.

With Leavel’s arrival, the “madness” begins.

At one point, she gives goofy Bonnie (Heidi Blickenstaff), Andy’s latest love, a puzzled look and asks, “Were your parents siblings?”

Bonnie’s the other scene-stealer. She not only coins malapropisms like a Restoration comedienne, she refers to herself in the third person.

Which raises another question: what does Andy, self-proclaimed intellectual and genius writer, see in Bonnie? Or his first wife Jane, N.R.A. queen, whose favorite color is camouflage?

And aside from their skills as writers, what does Mags see in Andy? He’s a mother-dominated, compulsive liar (in the vaudeville tradition of “dog and pony” shows). As played by Jon Patrick Walker, he’s also a narcissist who shouts most of his lines like a TV game show host.

These questions would pose fewer problems if Nicole Parker were less wonderful as Mags. The conflict between the co-workers gets spelled out too often (the book, Act one in particular, is needlessly explanatory, often after the fact). Parker specifies where she can, sings up a storm, and blazes across the finish line when “Mags Takes Flight.”

Except for Parker’s winning performance, the minor characters steal the show (Blickenstaff’s “Bonnie Doesn’t Get It” and Leavel’s “Problem Solved” major highlights). Eric William Morris adds funny moments in multiple roles. This bottom-heavy thievery wouldn’t happen a.) if the scenes between Mags and Andy weren’t so generic, predictable, and sometimes dull, and b.) if Andy were more sympathetic.