John Fugelsang is a reedy, not unattractive fellow with Kyle MacLachlan’s hair, Alan Alda’s voice, and Richard Lewis’s exasperated brow. If you know him at all, it’s probably from his two-year stint as the host of “America’s Funniest Home Videos” or from his talking-head duties on VH1. What you may not know is that he is also responsible for destroying two separate marriages. Marriages to God, no less.

This penchant for heavenly home-wrecking is discussed at some length in Mr. Fugelsang’s fitfully amusing solo show, “All the Wrong Reasons: A True Story of Neo-Nazis, Drug Smuggling, and Undying Love.” His parents — a former priest and a former nun — left their vocations to get married, and the notion of original sin, a central tenet of Catholicism, has a particularly firm hold on Mr. Fugelsang: “My parents had promised God I would never happen.” The Creator, he is convinced, hasn’t forgotten.

In a nod to John Leguizamo’s bawdier (and funnier) solo shows, Mr. Fugelsang charts his dogged efforts at sidestepping the baleful influences of his god, his folks, and his own worst instincts, never losing sight of the fact that the instincts exist largely because of the god and the folks. He describes Catholicism as “the shame machine,” and judging from the fraught holiday visit he uses as a framing device, the machine is firing on all cylinders within the Fugelsang family.

We join John on a recent Thanksgiving at his parents’ new home in Florida, where his father is recovering from a heart attack. John had ditched what he contemptuously calls his “prompter monkey” work on television a year earlier, leaving him with a renewed sense of pride but without health insurance. Pleading poverty has allowed him to continue putting off marrying Charmien, his girlfriend of 11 years, but his mother doesn’t buy it. And she’s not above using her infirm husband as emotional blackmail.

Not that Mr. Fugelsang can’t conjure up plenty of guilt on his own. “If you feel bad about something you did, that’s guilt,” he explains. “If you feel bad about who you are, as a person, that’s shame. But if you feel shame because you think God wants you to feel more guilt? That’s Catholic.”

What does all this have to do with neo-Nazis and drug smuggling? Well, nothing, and so Mr. Fugelsang shoehorns within this family drama a pair of extended comic monologues. First is the tale of his appearance on Bill Maher’s “Politically Incorrect” with David Duke, a confrontation that culminated with Mr. Fugelsang offering to sodomize the former Nazi and Klansman. This invitation was a bigger hit among the studio audience than at the Fugelsang home. He also recounts a near-disastrous attempt at transporting marijuana (intended for a friend with AIDS, he hastens to add) through the Orlando airport.

These anecdotes, along with his lingering feud with Catholicism, allow Mr. Fugelsang to show off his gift for free-associative erudition. Comfortably name-dropping everyone from Pope Innocent II to the Wu-Tang Clan, from Mookie Wilson to Elisabeth Kübler-Ross, he displays a restless intelligence that seems particularly ill suited to his old job introducing home videos of toppling grandmothers and hula-hooping kittens: “I have come to view Jesus the way I view Elvis. I love the guy, but a lot of the fan clubs really freak me out.”

Director Pam MacKinnon presumably had some involvement in coaxing these quips, tales, and factoids into something like a narrative, complete with not one but two feel-good conclusions. All the same, Mr. Fugelsang’s best material comes in self-contained, comedy-club-friendly packages. He has a great bit about the envy and animosity that his and Charmien’s non-married status inspires among their married peers, both male and female. And the “Politically Incorrect” sequence blends his quick-witted and pedantic tendencies well, although his self-evaluation midway through the taping as “an alternative-comedy god” comes across as both grandiose and, given the play’s overarching themes, a tad messianic.

Ms. MacKinnon’s staging remains mindful of her star’s preferred milieus; the New York Theatre Workshop stage has been stripped down to a couch on one side and a microphone on the other, with Mr. Fugelsang shuttling comfortably between the two. And when he pauses for laughs that don’t materialize, she has seen to it that new material is always at the ready.

Those silences occur more than Mr. Fugelsang might prefer: While his stories are usually amusing, many of them still have a bit of fat. What makes this more galling is that the glimpses we get of his parents suggest that a more interesting story is being ignored. His mother joined the convent immediately after high school and spent the next decade in Africa, ministering to lepers and to the sick. During this time, her hair turned white before she had turned 25. She peeled snakes from around bedposts and saw crocodiles pluck human babies from the riverbank. And all the while, a Franciscan Brother wrote to her weekly from Brooklyn and harbored a deep, blasphemous love.

Mr. Fugelsang is enormously respectful of them and of their love, but their relationship serves as little more than an object lesson for their conflicted son. Skirmishes with Klansmen and airport rent-a-cops can — and, in “All the Wrong Reasons,” generally do — make for diverting stories. But with conversions of this magnitude hovering on the periphery, mere diversions can prove awfully unsatisfying.

Until May 6 (79 E. 4th St., between the Bowery and Third Avenue, 212-239-6200).