Sideshow: Genius, and a swinger, too?

Stephen Hawking, now 70, has frequented a California swingers sex club for five decades, say a spate of tabloid reports. RadarOnline cites Eyewitnesses who say the 70-year-old Hawking, who runs the Institute for Theoretical Cosmology at Cambridge University and is considered to be the globe's smartest dude, is an active member of Freedom Acres in Devore, Calif. "I have seen [him] at the club more than a handful of times," Anonymous Source tells Radar. "He arrives with an entourage of nurses and assistants." (Nurses? Hawking is almost completely paralyzed due to a neurological disorder.) Adds Source, "last time I saw him, he was in the back 'play area' lying on a bed fully clothed with two naked women gyrating all over him." A Cambridge rep denies the report, in part. "It is not true Professor Hawking is a 'regular' visitor," Tim Holt tells the Cambridge News. "This report is greatly exaggerated. He visited once a few years ago with friends."

Teens belong to an alien species, so it's no wonder well-meaning human parents can't cope with them. Reese Witherspoon didn't think she could. "I don't know anything about teenagers, so I'm on a big learning curve here," Reese, 35, tells British TV show Daybreak about her 12-year-old daughter, Ava Elizabeth. (Ava and bro Deacon Reese, 8, were both fathered by Reese's ex, Ryan Phillippe

.)

"There's a little sadness as they're growing up and walking away from you," says Reese, "but it kind of changes the . . . dynamic. We have really funny dinner conversations now, and they know more about certain topics than I ever . . . knew."

The New York Post says premiere American novelist Nicole "Snooki" Polizzi, 24, lied when she denied recent reports she is carrying Jionni LaValle's child. Why? Sources say Snooki is waiting for a mag or TV show to pay her for exclusive rights to run the announcement. Snooki's rep proffered a "no comment" when USAToday.com asked about the Post's claims.

Sin City's (mega-)lounge singer Celine Dion has canceled all her shows until June to recover from a virus that's causing inflammation in her vocal cords. She's due to resume regular shows at the Colosseum at Caesars Palace on June 9.

Did greedy record execs fake Michael Jackson's voice to make a few (million) extra bucks from sales of MJ's posthumous album Michael? That's the claim reportedly made by MJ's daughter Paris Jackson, during a 2010 video chat with a group of friends.

"It's not him . . . the whole album isn't him!" Paris, 13, told her pals, according to TMZ, which says it has obtained snippets of the recorded chat.  Paris is said to believe the voice belongs to the singer Jason Malachi. Malachi and Sony have previously denied similar allegations.

Lifetime has green-lighted 10 half-hour episodes of a new "docuseries" (that's a reality show with a snap-on bow tie) about the glories of being named Bristol Palin

.

Daughter of onetime vice presidential candidate Sarah Palin, Bristol is a former Dancing With the Stars star, a single mom, and a poster girl for pro-abstinence groups.

Bristol Palin: Life's a Tripp will reveal "Bristol's real-life experiences growing into womanhood," says the cable channel.

Adele's 21 continues its dictatorial reign atop the Billboard album charts, selling 297,000 units this week, according to Nielsen SoundScan. It's been in the Top 10 for 22 weeks, second only to Prince's 1984 LP Purple Rain, which ruled the chart for 24 weeks. Whitney Houston's Whitney: the Greatest Hits is at No. 2 with 174,000. The band fun is at No. 3 with Some Nights, with 70,000 sold. Local alterna hip-hop act Chiddy Bang enters the national charts at No. 8 with its debut, Breakfast, with 31,000. Locally, the album is at No. 3.

   Agatha Christie's The Mousetrap - the world's longest-running play, in its 60th year in England - got a new surprise ending for the first (and only) time Wednesday night at the Walnut Street Theatre's current production. At the show's end, actor Dan Hodge, who portrays the owner of a guesthouse in the production, proposed to his unsuspecting girlfriend, actress Krista Apple, on the Walnut's stage.

About 1,100 audience members, also surprised, witnessed Hodge pop the question to Apple, who was in the audience and on break from a tour of the Walnut's recent production Proof. Why the public proposal? "I'm a huge theater history geek," said Hodge, "so there's really something exciting about the prospect of becoming part of the history of this major American theater." What's more, Apple's fave play - A Streetcar Named Desire - had its pre-Broadway tryout at the 203-year-old theater, on the same stage, in 1947. - Howard Shapiro
  

Tinseltown royalty Jennifer Garner and Ben Affleck, both 39, have welcomed their third child. Samuel Garner Affleck will balance out Bennifer's decidedly girly household: He joins sisters Violet, 6, and Seraphina, 3.

Philly-born musician Kenny Gamble will be one of three citizens awarded next month by the National Public Housing Museum in Chicago for their work with inner-city communities. Gamble will be honored for his "lifelong commitments to housing, social justice and equality," the org says in a statement.

Marston Hefner, 21, son of Playboy founder Hugh Hefner, was charged on Wednesday with spousal or cohabitant battery, accused of assaulting his gf, 21-year-old Playboy Playmate Claire Sinclair during a domestic dispute Feb. 12. He could face up to a year in jail.

Former child star Tatum O'Neal, 48, who has battled addiction for years, is back in rehab following a relapse, says RadarOnline. "Tatum made the decision to voluntarily check into rehab after having a relapse about a month ago when she began using cocaine again," Anonymous Source tells the gossip site. Tatum isn't the only one of Ryan O'Neal's issue with drug problems. Her 27-year-old half-brother, Redmond, is in court-ordered rehab for heroin addiction following arrest for drug possession.