A number of Hollywood A-listers were on the star-studded guest list for Reese Witherspoon and Jim Toth’s nuptials this weekend. And two of them caused quite the stir – just by arriving together: Scarlett Johansson and Sean Penn.

Johansson, who is a client of Witherspoon’s new hubby, was on the guest list, but supposedly no one knew Penn would be her “plus one.”

“Turning up at a wedding with your boyfriend is definitely a huge statement, especially that wedding. What it’s doing is announcing to the whole of Hollywood that they are serious,” a source close to the former Mrs. Ryan Reynolds told PopEater’s Rob Shuter.

“Scarlett is head over heals in love with Sean,” the supposed friend went on to say. “She normally tries to hide away from public attention, but when she’s with Sean she doesn’t care.”

Tongues have been wagging for months, ever since the two were spotted together after Johansson’s split with Reynolds. Reps from both sides have tried to dispel the rumors that the 26-year old actress and 50-year old actor were romantically involved, despite plenty of evidence to the contrary. The pair – already being referred to by the unfortunate nickname “S-Squared” – has been seen dining together, not to mention making out, on more than one occasion. And there was that quick trip to Mexico earlier this month…

Now it seems, their relationship is official. And rumor has it, another trip is in the planning – this time to Haiti, where Penn is actively involved in relief efforts.