Review: Will Arnett shines in so-so ‘Is This Thing On?’

That’s because director Bradley Cooper wants to probe other things — like the demise of the man’s marriage and the start of a new career.

Arnett’s Alex doesn’t go through the angst of “Marriage Story,” but comes to the same conclusion as his wife (Laura Dern, who appears in both films): Their marriage has run its course. They agree to separate and, on his way home, he wanders into a comedy club and appears on stage in exchange for admission. There, he opens a vein and realizes he likes the therapy. One set leads to another and soon he’s able to mine his life for more humor.

In time, his wife comes to see him (toting Peyton Manning, no less) and laughs, even though she’s often referenced.

Where this heads is anyone’s guess, but Cooper makes sure the shift unfolds naturally. Arnett is key to that transition. He’s great on stage (of course), but he handles those quiet “dad” moments with great aplomb. There’s a sadness laced with hopefulness that makes this a more realistic look at separation. Dern is great, too, particularly since she’s mining the life of a former Olympian and discovering what’s next for herself.

Cooper stuffs the film with plenty of friends (try to spot who’s in the mix) and moments that seem cobbed from life. Where he falls short, oddly, is on stage. Those standup moments are like the ones in “The Marvelous Mrs. Maisel” — often off-the-cuff, not crafted. Considering Alex moves up the ranks, they shouldn’t all be streams of consciousness but moments that resonate with those who come to see him.

Other films about comedians, like “Punchline,” had similar problems. Telling the story of a budding career could happen offstage, never actually on it. Combining the two puts pressure on one or the other.

Here, the domestic story wins, but “Is This Thing On?” isn’t a look at comedy. It’s an opportunity for Arnett to show what a great dramatic actor he can be. Now, he just needs the right platform.