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MR. SMITH GOES TO CONFESSION: Confessions of a Teen Idol started out in longhand as a tell-some, then it struck Rex Smith it was really a musical autobiography, so he quickly rearranged his stories into a nightclub act and tried it out for eight weeks in San Diego. The result arrives at 54 Below Aug. 26 at 9:30 PM. He sees it as an act of many hats: "I've been lucky enough to be rocker-teen idol-superhero-primetime/daytime/Broadway/movie star, and I wear each one of those hats and take you on a 40-year journey to wherever I am that night.

"I do bits 'n' pieces of my early rock 'n' roll when I was touring with Ted Nugent, into 'You Take My Breath Away' and 'Forever,' songs that took me around the world. I found the actual videos from the old days in my garage and use that in the act."

To be sure, he does a proper drum-roll for his Broadway credits (The Pirates of Penzance, Annie Get Your Gun, Grand Hotel and The Scarlet Pimpernel), and he was Diahann Carroll's leading (kept) man for a 650-performance Canadian tour of Sunset Boulevard. "That's where I met my oldest son, Brandon," he said casually.

Smith met the 16-year-old while signing autographs. "His mother had passed away, and she had told him, 'Your father is Rex Smith.' One look at him — it's undeniable who he is. Now, I have a grandson with him. Dickens couldn't write this." In recent years, he has been hanging out in California suburbia, Little League-coaching and playing patriarch to five kids and a two-year-old grandson. He's three weeks away from 59, looks nowhere near that and could pass for Sitcom Dad if the call ever goes out for a better-looking Dennis Leary — a kind fate for an old rocker.

REBECK AND CALL: The other day, racing to the press meet 'n' greet for You Can't Take It With You at The Duke on 42nd Street, both Johanna Day and Reg Rogers experienced a déjà vu moment. Now playing in the same building is Poor Behavior, the Theresa Rebeck play which they world-premiered in 2011 at L.A.'s Mark Taper Forum with Sharon Lawrence and the late, great Christopher Evan Welch.

In the current New York edition, their roles are played by Katie Kreisler and Brian Avers. The cuckold is easy to spot in this one: He's the one with morals and shoes.

PORNUCOPIA: "I've been waiting for somebody to pick up this title," I told writer-director Neil LaBute about the sex comedy he will be world-premiering for MCC next month at the Lucille Lortel, The Money Shot. "Pick it up carefully," he advised. The play is his first volley at the porn industry, LaBute noted. "It's one set, high in the Hollywood hills, two couples getting together to talk about a love scene that's coming up and what they can and cannot do — the boundaries of what they are able to do within that love scene. One couple is a same-sex couple, and one is a heterosexual couple, but the guy is quite a bit older than his young wife."

There's a specific cinematic reference point for the play — a 2001 French film called "Intimacy," which featured Kerry Fox and a fiercely full-frontal Mark Rylance. It's one of many controversial films helmed by Patrice Chereau, who died last year at 68. "Chereau asked his actors to copulate for a piece of art. When I heard how that came to be — how they were actually asked to marry life and art — I was intrigued. The director was interested in actually having sex on screen. That sorta echoes my interest in Terry Southern's 'Blue Movie' — the whole idea of where art stops and life begins. I try to touch on a number of different things people face in that situation."

THERE'S A HITCH: On the one hand, there's only one set. On the other hand, it's A Very Big Set. That's the major hurdle looming ahead for the stage version of "Rear Window," Alfred Hitchcock's 1954 thriller about an invalid voyeur who witnesses a murder. Keith Reddin is doing the adaptation, "but that's down the road a piece," cautioned the designated director, Terry Kinney. "We're still developing the script."

DOUBLE IDENTITY: "Mad Men" leading man Vincent Kartheiser and Larry Pine, last seen on Broadway in Casa Valentina, will star in Billy and Ray at the Vineyard Theatre. Gary Marshall will direct the story of Billy Wilder and Raymond Chandler during their contentious creation of the film noir classic, 1944's "Double Indemnity," and he also has his assistant director in place — the same one he used for the play's world premiere in L.A.: Joseph Leo Bwarie, who, by night, is currently playing Frankie Valli on Broadway in Jersey Boys. "He started at my theatre in L.A., The Falcon, playing Chochi in the Happy Days musical," Marshall said, "but he's a good director, and he helped me with the film noir lighting for this."