Sean Penn Scarlett Johansson Hooking Up?

Is ScarJo doing Spicolli? Reps on both sides deny it, but If all the tabloid reports are to be believed, Sean Penn is the fourth guy Scarlett Johansson has hooked up with since her split from husband Ryan Reynolds last December.

Scarlett, 26, and Sean, 50, are both freshly single (Sean ended his 14-year marriage to Forrest Gump’s Robin Wright in 2010), and according to Us Magazine, the May-December lovers are totally doing it. Loose-lipped informants say the pair began their fling in January, when Scarlett was in Los Angeles filming We Bought a Zoo with Matt Damon. She approached Sean because she was interested in helping out in earthquake-ravaged Haiti and a romance soon blossomed.

“Their first hook-up was in Scarlett’s Bungalow,” an insider told the mag. “Scarlett first reached out to Sean when she was planning to visit Haiti with Oxfam. She knew Sean was living there in a tent and turned to him for advice.”

Obviously the next logical step was for them to hook up!

“Scarlett’s smitten with him,” adds the source.

Bologna, says a rep for Johansson.

“Scarlett and Sean are not dating – they have been friends for years. Nothing more, nothing less,” the publicist said in a statement Thursday. “They have been talking over the last few months regarding Haiti Relief and Scarlett’s upcoming trip to Haiti as Oxfam’s Global Ambassador.”

Sean was last romantically-linked to Sports Illustrated model Jessica White. While Johansson has allegedly been quietly rekindling her rumored relationship with Justin Timberlake.