To make their first bonafide Hollywood debut as a couple, Scarlett Johansson and Sean Penn picked the most romantic event possible: a wedding!
Although the couple were caught packing on the PDA during a romantic trip to Cabo San Lucas, Mexico, Johansson, 26, and Penn, 50, have tried to keep their fledgling romance quiet closer to home.
But the duo were finally ready to go public, at least among other A-listers, on Saturday at Reese Witherspoon's wedding to Jim Toth, a CAA agent who represents Johnasson among many others.
The hot new couple watched Witherspoon, 35, wed Toth, 40, at the actress' Ojai, Calif. home alongside such celebs as Renee Zellweger, Tobey Maguire and wife Jennifer Meyer, Robert Downey Jr., Matthew McConaughey and love Camila Alves, Alyssa Milano, Colin Hanks, Isla Fisher and hubby Sacha Baron Cohen.
When the farm-style bash was over, Penn and Johansson stopped by Jimmy's Bar at Ojai Inn and Spa for a nightcap and late-night grub.
According to an eyewitness, Johnasson (wearing a low-cut black dress, black shawl, and red lipstick) was rattled by all the stares at the packed bar. "This is so terrifying," she muttered to suit-clad Penn, who held her hand as he led her to their seat.
After the duo ordered gin and tonics, pizza and a club sandwich, they were joined by actor Tom Hooper and a female pal. The Iron Man 2 star gushed about the wedding -- and the cake! "It was so great!" she told the table.
After the table cleared, she sat in Penn's lap -- and they made out in full view for 15 minutes, according to the observer.
An insider recently told Us that Johansson, who split from hubby Ryan Reynolds last December is "head over heels" for Penn.